Great to hear it's working for you. I've long suggested that the cheap Chinese lenses are a lot like the high-end vintage lenses from the SLR film camera days - both had simpler optical designs and simpler coatings. The only challenge is how good the lens is wide open, but if it's enough for your application then you're all good!
Same for me.
I have saved power grades for each camera that convert from camera colour space to Davincis log space, and a few Timeline power grades that apply a few variations of film emulations. I just pull all the footage into a timeline, apply the power grades, and then adjust exposure on any clips that need it (I use ETTR so this is normal for me) and mostly I'm good. The wider DR of the GH7 and iPhone 17 Pro means that the images are less crunched and therefore respond nicely to a film emulation contrast curve and so need a lot less fussing than the GH5 ones did.
I standardised on 58mm filters as that's the largest size that fits most of my lenses. Actually about two thirds of my lenses have that size natively and for the ones I use a lot that don't have that I bought dedicated step-up rings and just have them permanently attached.
I have a K&F Concept True Color Variable ND2-32 (1-5 Stops) as my main vND and recently bought a NiSi IR ND8 (3-Stop) fixed ND to stack on it if the 5 stops of the K&F aren't enough (5 stops is enough for full-sun at F5.6 but wider apertures than that will require more). I wanted to just buy a nice 5-9 stop one but I have a Tiffen? 4-stop filter and when I paired that with the 1-5 stop I got all kinds of IR pollution on the iPhone, so I knew that anything more than 5 stops needed IR filtration too, and I couldn't find anything that had it.
I had to buy an 82mm one for the front of my Sirui anamorphic adapter, but got a cheaper Neewer 1-5 stop which seems to work ok, although that one I only shot at night and colour fidelity is less important for that stuff.
I also bought a few lower-quality 1-9 stop vNDs in specific sizes for when I wanted to keep the lenses as small as possible, so I got a 46mm one for the 14mm F2.5 pancake lens which lives on my GX85, and a 40.5mm one for the 17mm F1.4, which I had thought might be a good low-light lens for the tiny GX85 Super-16 setup but I haven't shot anything with that combo yet.
Funny how people end up with similar solutions!