Game runs well, other than the known stuttering which is a problem with the PC port regardless of hardware performance. Regarding the 30fps cap, if millions of people could play this at 30fps on PS4 then you can definitely have fun on the Steam Deck at 30fps. At 30fps you can run at native resolution without any upscaling or frame gen technology, you get pure frames and the game looks great!

I recommend these Display settings:

• 1280x800
• Upscale Off
• FOV 80
• Adaptive performance FPS Off
• FPS limit unlimited
• Refresh rate 60 Hz
• Vsync Off

Graphics settings:

• Start with medium preset
• Disable motion blur
• Enable TAA anti-aliasing

I didn't test it fully but you might get away bumping Textures/Model quality/Anisotropic filtering to High.

Lastly, remember to run the game in 60 Hz in the Steam Overlay settings.