So when using this test video there is noticeable judder at 24fps. Playing back at 1.25x (30fps) is as smooth as you'd like. Performance is very similar to an S21 Ultra if that's a useful reference. Of course, this is a long horizontal panning shot, which I know to be the worst for judder. I'd bet my LG C1 would struggle with it.
When watching modern films, I find that these kind of shots occur less. I can't say I've really noticed judder whilst watching films on this device. Clearly it does happen, but it's not something that has bothered me personally. I would say I'm the kind of person to notice any inconsistency in presentation of video, be it judder, stutter, bad frame timing, micro-stutters in games, low bit rate etc... So make if that what you will.
If I were at home if film it for you, but there's very megre Internet where I currently am.
The screen is vibrant, bright enough and has OLED contrast.
Sound is OK, nothing to write home about, but it's on par for a device this size. If you go the Lineage route, I'd recommend using Flat Equalizer to raise the bass and some mids for a fuller sound more akin to the One UI tuning.
I use this for F1 (50fps), football, movies, TV, and YouTube and I really like it. For the £80 I spent, I'm delighted. Only get 5 or 6 hours SoT, which might be a downer, but it's an old used battery so what else do you expect?