Here are the settings I use in Oblivion Remaster with my Steam Deck for smooth gaming.
Widow Mode Borderless
Display 800x1200
Vsync Off
Show FPS/Vram Off
Brightness 4
FOV 1st Person 82
FOV 3rd Person 82
Motion Blur Off
Screen Space Reflect Off
Quality
View Distance Low
Effects Quality Low
Foliage Quality Lowest
Shadow Quality Medium
Global Illum Low
Texture Quality Medium
Reflection Quality Lowest
Post-Proc Quality Lowest
Hair Quality Medium
Cloth Quality Ultra
Lumen Hardware RT Off
Lumen Software RT Low
Advanced
Anti-Aliasing TSR
Upscaling FSR
FSR3-Mode Performance
FSR3 Sharpness 100
FST3 - Frame Gen Off