rimpamposh

I'm surprised the samyang 24 is smooth, my 85 is rubbish, which is why i wasn't tempted on picking any more of these (also large).
Now, the contax lenses, very smooth.

Allow me to explain further rimpamposh, because that video is explaining the situation in my opinion in a twisted and counter intuitive way IMO.
Lets look at the RGB waveform of this NX1 file:

If you look at the top of the waveform it seems the highlights are clipped. However pay attention to the bottom right Clamp Signal checkbox that is checked on and that I circled in green. That clamp signal checkbox, clamps the display of the highlight. It does not DISPLAY in the waveform scope the highlights above the 100 line. However the information is in the video file, it is simply not displayed because that checkbox is checked.
 
Lets have a look at what our waveform looks like once we uncheck it:

As you can see we have more highlight information visible in the waveform scope than what was previously displayed. 
And that is all that has changed, the clamped highlight information above 100 is now displayed in the waveform monitor only. In our video it is still out of range because it is above the 100 line, so in our video those highlights are still clipped. How do we recover that information and unclip the highlights in the video? 
This is where in the video he says to set the 235 number. You do not need to do specifically do that, and you can do it with a variety of tools. And that specific amount will not be adapted to every situation. All you want to do is bring the highlights down. That is all. In this instance I did it as following:

You can do it in different ways. Hope it helps.

Even in NX1 is 1080p mode very much sensitive on ISO/framerate. 
My experience (I had always smart range ON but I have not make any comparsion how it affect image quality):
1080p60 - maximum usable ISO for me is ISO 400 and everything above is "smeared to hell and blotchy"
1080p120 - maximum for me is ISO 200. Decrease in quality is visible even on A7SII and GH4, still NX1 seems to be best even on ISO 1600 - see here https://www.youtube.com/watch?v=Ek2l3d6hVQ0
4k30p - fine and no problem here - everything is quite as expected. Image become little smeared since ISO 1600
Summary - I use 1080p modes only with fast lenses or in bright light... 

The jerky motion could be caused by lens stabilization, especially since you say it's not dependent on shutter speed.
As for the sharpening, that is kinda the normal behaviour of simple spatial sharpening. If you take a blurry picture and apply x amount of sharpening, the effect seems to be small. Take a sharp picture and apply same sharpening and the effect seems very strong.
Therefore the jerky motion + sharpening will accentuate the jerkiness even more.

The jerky motion could be caused by lens stabilization, especially since you say it's not dependent on shutter speed.
As for the sharpening, that is kinda the normal behaviour of simple spatial sharpening. If you take a blurry picture and apply x amount of sharpening, the effect seems to be small. Take a sharp picture and apply same sharpening and the effect seems very strong.
Therefore the jerky motion + sharpening will accentuate the jerkiness even more.

The jerky motion could be caused by lens stabilization, especially since you say it's not dependent on shutter speed.
As for the sharpening, that is kinda the normal behaviour of simple spatial sharpening. If you take a blurry picture and apply x amount of sharpening, the effect seems to be small. Take a sharp picture and apply same sharpening and the effect seems very strong.
Therefore the jerky motion + sharpening will accentuate the jerkiness even more.

Well, since there is basically no useful info on the net about video smart range on these cameras, I made a quick test with my nx500.
Basically the exposure is lowered by about 0.4-0.6 stops. So let's say I set shutter to 1/50. With dr on I get iso 250, with dr off I get 400. Now there is something odd about its behaviour. With dr on the clip starts darker but it gradually gains brightness, in about 5 seconds to about the same brightness level as dr off. A bit brighter even I'd say based on my 2 quick tests.
But the highlights gain less brightness than the rest. Based on my initial impression you get a bit flatter image, and I haven't noticed any bad side effects. I didn't test in challenging conditions that might create banding (so the question remains if this method is better than reducing contrast or not). This is with nx500 which doesn't have gamma dr.
I wouldn't write it off just yet, may be pretty useful for nx500 users.

Well, since there is basically no useful info on the net about video smart range on these cameras, I made a quick test with my nx500.
Basically the exposure is lowered by about 0.4-0.6 stops. So let's say I set shutter to 1/50. With dr on I get iso 250, with dr off I get 400. Now there is something odd about its behaviour. With dr on the clip starts darker but it gradually gains brightness, in about 5 seconds to about the same brightness level as dr off. A bit brighter even I'd say based on my 2 quick tests.
But the highlights gain less brightness than the rest. Based on my initial impression you get a bit flatter image, and I haven't noticed any bad side effects. I didn't test in challenging conditions that might create banding (so the question remains if this method is better than reducing contrast or not). This is with nx500 which doesn't have gamma dr.
I wouldn't write it off just yet, may be pretty useful for nx500 users.