Alright, the stuttering is not my forte for troubleshooting. It could be from the driver but it could also be just the compatibility layer or myriad of other factors. I don’t play those games myself too. However, you can try searching for protondb to see the state of the game support on linux. Here is for Elden Ring for example. And be sure to actually check the review as it really reflects the state of games. You can also try looking for those with the same hardware and see if they comment on any issue. That can at least help weed out some potential problems.
Lastly, the brightness issue. Can you describe it in more detail? Like, does it happen when you are turning HDR on or is it happening regardless of HDR? And what does it mean the brightness is all over the place? Is it happening when you are consuming video content? I have an OLED for example, and the black is always the same regardless of the brightness. So are you sure it isn’t from the content itself?