Mark Romero 2

Lenses can be matched in post if you're willing to put in a bit of effort.
Here's an example where I match a Samyang to a Lomo...  unedited:
and matched:
If you put a look over the whole film you'll also help to even things out too.

It does look great in low iso and with sharp glass, but it's not as sharp as the fullframe 6k downsampled to 4k where the detail just pops off the screen, in lowlight the noise is approximately 2/3 of stop noisier in my experience.

If you need continuous autoffocus then I agree with @Thpriest that you would do better with either Sony or with Canon.
If you go with Canon make sure it is a model that has Dual Pixel autofocus in video. My understanding (and I could be wrong so do some research) is that some Canon cameras that claim to have dual pixel autofocus might only have it at certain resolutions. 

At this current pandemic it's kinda dumb to invest huge money for wedding business 

And, from what I understand is that this guy wants to start in Wedding videos and move to doc and commercial work.
Blowing it all on just a body.... doesn’t make sense.
Equipment cost < Business Profit
Look at high end equipment later. Start getting customers first... start charging a rate that covers your hours put into it + equipment rental rate (estimate).
If you get enough customers then invest in equipment.

I did the same thing, I got the Sigma adapter and can now use all of my EF mount FF lenses with no problem on the S5 and out of all of my lenses including APS-C lenses only the EF-S 10-22mm does not work.
The focus peaking kind of sucks, very hard to see and for me a lot of the time its just not visible at all and combine that with the fact you can't zoom in to check focus while recording  and the focusing situation when using EF lenses in general isn't that great; I am sure the native lens experience is better. As long as you aren't filming with a razor thin depth of field and not filming anything fast paced its workable but definitely not great.

New firmware announced by Panasonic for the S1 (as well as some for S1R and S1H) coming November 24th.
The good news is that the new AF system (implemented in the S5) is coming November 24th. Red recording status frame indicator (Yeah!!!).
They also announced that firmware is coming in the first half of 2021 for the S1 which will allow for 5.9K RAW over hdmi, and 5.9K / C4k internal recording. Finally 4K 60p internal will be 10-bit 4:2:0 instead of current 8-bit 4:2:0
All the same, I am thinking of either "downgrading" to an S5 or instead going for...
...an R6. 

Damn my Panasonic S1 is getting a huge upgrade next year. Prores RAW out....... 

Feeling good about picking one up for $1300. 

True they do not have a dedicated video camera, though they do offer dedicated video lenses, but based on the OP's original question and further responses, this is someone looking to get into photography/video on a relatively low budget rather than expecting to shoot even an indie movie.
The Fuji XT3 produces excellent 4k, 10 bit internal video, full-frame quality matching stills and the XT4 ups the game further with IBIS and back up insurance of being able to write to both cards which few can do. As a starting out system or moving up from 4/3rds, it's excellent.
Weak point is the lack of video-orientated lenses with AF though several of them are more than good enough in this department, particularly the; 18-55, 16-55, 50-140, 23 f2 and 50 f2.
It's the system I have been used for 50+ jobs since the XT3 came out (and XH1 previously) but have just moved the Lumix S5 for a number of reasons that are not critical of the Fuji system.
There really is not a bad system though, whether it be Nikon, Canon, Sony, Panny or Fuji as each have strengths and weaknesses and will suit certain users better than others.

That seems kind of strange...
On the S1, if you put an EF-S lens on the MC-21, the camera will automatically default to APS-C mode, both for stills and for video. In fact, you can't get out of APS-C mode.
The exception to the above is something like Tamron EF-S lenses since I guess even their crop lenses had the EF mount. 

At 3k, I think you are going to struggle to get 2 cameras such as an A7iii and a Black Magic and lenses etc, so why not just consider one single hybrid and one decent zoom?
At 3k, my pick right now would be Fuji XT4 with battery grip + 16-55mm f2.8 and you'd have some change left over.
Right there you have got shoot all day capability due to the already good in body battery and with added grip power...which nicely balance out the 16-55mm f2.8...which has a FF focal range of 24-83mm...produces excellent stills and exceedingly high video quality straight out of the box.
I honestly think it is the least compromised hybrid available right now, all factors considered including price.
My other pick would be the Lumix S5 which is what I have chosen as my hybrid, but for me, I'd prefer to shoot this as a pair with some fast primes...which are coming shortly, but a pair of anything (except maybe XT3's) will bust your budget.
My third and final option would be a pair of XT3's, with the 23mm f2, 50mm and 90mm f2 which would just sneak into your budget if you bought nearly new with the only real caveat being no IBIS or OIS with any of that so maybe less useable on the video side without mono or tripod.

I'm an owner of an EM10III and 3 lenses, but typically only use one (manual prime) ...and I make films all the time, so my perspective is that almost all this gear on the market pretty much works great if you know what you want and how to get it.

I like @Geoff CBsuggestion of getting an a7 III. you can probably buy one used for around $1500 (maybe less???) as the price NEW just dropped to $1700.
If you decide you want to go 10-bit, then there is the Fuji X-T3 / X-T4. On the other hand, if you shoot 8-bit Cine 4 on the a7 III with the contrast down (or shoot in HLG) you are gonna get about as much dynamic range as the X-T3 in FLOG.  
I like my Panasonic S1 a lot, but it is heavy and the autofocus is second-rate. I might "trade down" to an S5 since it has better AF and is lighter, and since I normally use Lens image stabilization to avoid warping when on a gimbal. Lenses for full frame panasonic cameras are expensive though. They are VERY GOOD lenses for video, but expensive. 

Congrats on being close to wrap!!! The stills look good.

We can help you better if you let us know WHAT you want to photograph and what you want to film.
For example, if you will be shooting sports (both photos and video) you will probably want a camera with really good autofocus and a high fps. 
If you are shooting travel videos, then a video camera with a really wide dynamic range, good low light and more color depth, yet somewhat portable might be a good idea.
If you are shooting documentaries, maybe a camera that would be a more streamlined "run and gun" camera might be be better. 
If you plan to shoot photos and videos of weddings, you might have a different need than other areas. 
Also, if you are going to shoot with two (or more) cameras at the same time, it might be best to get two of the same cameras so that it is easier to match the footage (make the colors look the same) from both cameras.
It looks like in the past you MIGHT have owned a GH4 and / or a GX85, right? (I just looked at your content history and it looks like you brought up some topics related to those cameras). If so, do you have a collection of M43 lenses???
 
 

That shit also drives me nuts.

Had this happen in town on the showgrounds in the middle of an oval. My third or fourth flight, nobody around except a few blokes from the mens shed who wanted a demo. i had an all clear ready to take off, sent it up about ten meters, then the warning box popped up scared the crap out of me. Cant doing nothing till you click ok. I was in beginner mode which limits you to about thirty meters. So i wasn't doing anything to ambitious, Very annoying. Probably wont send it up anywhere near town in future lol. Don't need the aviation authority bashing down any doors 🙄

I own the S1H and the S5. and there are a a whole lot more issues than you think!
The 8-bit stuff is only 4:2:0, and it's still H.264, not H.265. The same issue exist for the S1H, but we don't care because we don't have time limits. The 1080p VFR stuff is completely wrecked. The 100Mbps 1080p MOV files have been replaced with 28 Mbps MP4 trash. The timecode feature is a complete waste. If you can jam sync it, or get a jam from it, what the hell is the point? The only thing between the S5 and the S1H that is the same is 4K 4:2:2 150Mbps IPB in 24p and 30p everything else is 8-bit 4:2:0. If you buy this cam, do it knowing you are going to add a Ninja V for ProRes RAW. Other than that get the S1H. Battery life is good though. But with the limitations, don't think that this is gonna be a killer B cam, because what it can do is too limiting. Maybe if you think of it as a FF GH5 with full V-Log for gimbal work, that will meet your expectations.

If you don't care about: timecode, unlimited record times, a more substantial build, slightly more usable screen configuration, top LCD, better EVF (I never use it for video anyway), then I would get the S5. 
I don't notice a huge difference between 400 and 150 10-bit recording, so you should be fine there. Can always get 6k or ProRes Raw (soon) or All-I ProRes recording with an external recorder.

I haven't used the S5 yet, but I do own and have used the S1H for the last year. I love the camera. For me, the biggest advantages are timecode (a must for my doc work when I have external audio), the All-I 400Mbps (sometimes required), and the unlimited record times. The ProRes Raw is great, but the S5 will be getting that soon.
Otherwise, I think the S5's more compact size, better AF (though the S1H is confirmed to get it), and the already amazing 10-bit 422 150Mbps codec that I most often use on the S1H anyway, make it a pretty compelling option. 

DJI software drives me crazy sometimes.
There have been times where I check ahead of time to make sure that no Unlocking is needed in the location I am going to shoot.
Then when I show up, the app is telling me I need to unlock that location. Of course, it is out in the boondocks and I don't have cell service, so I can't unlock the location by phone.
Then when I get home I look again and confirm that NO UNLOCK is needed for that location.
The other issues I have is where the "checkbox warnings" (I don't know what they are called, but they ask you to confirm that you are authorized to fly in that area and that you accept the responsibility to fly there), will pop up NUMEROUS times during the course of a flight. Literally, they will pop up 20 times during the course of one battery when i am flying in an area less than 100 meters square. Constantly having to consent to their requirements when trying to film drives me crazy.

DJI software drives me crazy sometimes.
There have been times where I check ahead of time to make sure that no Unlocking is needed in the location I am going to shoot.
Then when I show up, the app is telling me I need to unlock that location. Of course, it is out in the boondocks and I don't have cell service, so I can't unlock the location by phone.
Then when I get home I look again and confirm that NO UNLOCK is needed for that location.
The other issues I have is where the "checkbox warnings" (I don't know what they are called, but they ask you to confirm that you are authorized to fly in that area and that you accept the responsibility to fly there), will pop up NUMEROUS times during the course of a flight. Literally, they will pop up 20 times during the course of one battery when i am flying in an area less than 100 meters square. Constantly having to consent to their requirements when trying to film drives me crazy.

Shot on the S1 with a 1/8 black pro mist (side interview shot is GH5) and some 16mm grain added in.
Heavily graded but if you have a bit of color grading knowledge then the S5/S1/S1H is a big step up from GH5 (not to mention low light capabilities). I think the v-log on the S series has a more organic quality than any of Sony, Canon's, Fuji's current offerings (less sharpening).
Just bought the S5 as a 2nd camera so look forward to testing that out.
 

Can you put a gopro on a separate gimbal and mount the whole thing on the car? 
I just don't understand how a camera mounted on the hood of a car won't be affected by vibration from the engine, and more importantly, by wind buffeting.

10bit is more important than 4K60
And yeah, hope it doesn't have a 10 minute limit like some Fuji do! (I could "live with" 30 minute limit)