80% resolution scale, everything on low runs for like 3,5hours, can sometimes (mostly cutscenes) drop to 45-50

Launch with Proton Experimental to improve frame rate in cutscenes 
Manual GPU Clock: 1400 MHz 
Scaling Filter: FSR 
FSR Sharpness: 3 
Resolution: 1024x576 (Game does not support 16:10) 
Frame Rate: Variable 
V-Sync: Off 
Rendering Method: Normal 
Rendering Scaling: 100% 
Texture Quality: Low 
Texture Filtering Quality: Low 
Mesh Quality: Low 
Alti-aliasing: FXAA+TAA 
Motion Blur: Off 
Effects Quality: Low 
Shadow Quality: Minimum 
Shadow Cache: On 
Ambient Occlusion Type: HBAO+ (Variable)
Bloom: Off 
Lens Flare: Off 
Volumetric Light Quality: Low 
Screen Space Reflections: Off 
Subsurface Scattering: Off 
Chromatic Aberration: Off 
Color Range: SRBG 

Framerate will tank in cutscenes and ruin the audio sync if you set the TDP limit and GPU clock any lower than recommended, but if you don't mind then you can set the TDP limit to 8 and GPU clock to 1000 MHz. Just know that if you do that, you have been warned. 

The game surprisingly still looks good on minimal settings. 

UPDATED :-

⭕  optimized settings for DEVIL MAY CRY 5 (better image quality than the default):-

☀️ got tested on steam deck oled (steam os  3.15.19
proton 9.0-2)

🛑 quick acesess menu settings :-

❇️ screen fram limits (60hz)
❇️TDP LIMIT = OFF
❇️Manual GPU clock = OFF
❇️scaling mode ( auto)
❇️scaling filter ( liner)
❇️sharpness ( 0 )

🛑in game settings :-

❇️aspect ratio (16:10)
❇️resoultion (1280 x 720) 
❇️refersh rate (90hz)
❇️window mode ( window )
❇️ frame rate ( varible)
❇️ v sync ( off)
❇️ rendring method ( normal)
❇️ resoultion scalling (120)
❇️  texture quality ( low)
❇️ texture filtring quality ( ultra)
❇️ mesh quality ( low)
❇️ anti-aliasing ( FXAA+TAA)
❇️ motion blur ( OFF)
❇️ effects quality ( high)
❇️ shadow quality ( high)
❇️shadow cash ( off )
❇️ ambiant occlusion type ( HBAO+)
❇️ bloom( off)
❇️ lense flare (on)
❇️ voulmetric light quality ( low)
❇️ screen space reflection ( arible)
❇️ subsurface scattring ( varible)
❇️ chromatic abrasion ( off)
❇️ color range ( SRGB)

🎉 results

stable 60 fps but with much better image quality and clearness than the default settings 
cutscenes FPS is not stable

#steam_deck_optimized_settings