Chromatic aberration, film grain and kinetic blur set off. FSR 2 with quality mode.

Consistent 40FPS
Make sure to lock FPS in SteamOS to 40hz.
Display options:
AA Mode = TAA low
Upscale Type = Nvidia NIS
Upscale Mode = Nvidia NIS Quality
Sharpness = .5
Video: (Set to medium and change below)
Material Quality and Texture Quality = High
FOG, Sky, Foliage, view distance, and Population = Low
Consistent 30FPS
Same as above but change view distance to medium or if you want better graphics experience leave view distance as low and change post processing to high. Make sure to lock FPS in SteamOS to 30hz. 
NOTE: Changing post processing will give decent performance in indoor and nighttime. In open areas on parts of Hogwarts and Hogsmeade frame will dip. 

Windowed mode, FSR 2.0 upscale sharpness 0.9 quality, texture settings medium, everything else low. Turn off motion blur, depth etc.. If possible turn off fog (watch youtube how to do it), this can increase like 20mins play time and give much stable 40fps framerate. Game is gpu power demanding, so make sure you install cryoutilities and increase vram to 4gb and everything else suggested for more gpu performance. If anyone else saying this game can run lower than 20 watts, well they are lying because even at 480p 30 fps, i still cant lower it down to less than 20w all the time (16-22w, and indistinguishable character faces)