My Steam Deck settings:

Overlay Frame limit: 30

Resolution: 1280x800

V-SYNC: Double Buffer

Fullscreen: On

Exclusive Fullscreen: Off

Aspect Ratio: 16:10

Motion Blur: On

Screen Effects: Off

Texture Quality: High

Texture Filter: 8x

Hair Quality: TressFX

Anti-Aliasing: FXAA

Shadows: Normal

Shadow Resolution: Low

Level of Detail: Normal

Reflections: Normal

Depth of Field: Normal

SSAO: Normal

Post Processing: On

Tesselation: On

High Precision: On

Just to note that my goal for this game is to have the best image quality with very rare FPS dips below 30 for very brief period of times. I even experimented with lowering the res to 576p and using the Deck's overlay FSR. I did manage to hit higher average FPS with that but FPS lows were about the same as the native 800p. Another thing to note is that pre-rendered cinematics with this game is 30 FPS so you'll get uneven pacing on cinematics if FPS limiter isn't evenly divisible by 30.