Steam Deck Optimized Settings
The only way to see an average performance of 30 frames per second on your Steam Deck is to set everything to "low," Textures to "medium," Texture Filtering to "high," and FSR 2 to "Performance."
This will make the image quality go down the drain, and you will experience sub-30 FPS frame drops at regular intervals, with some scenes featuring huge enemy hordes beating the hardware to a pulp and dropping the frame rate to below 20 frames per second.
Battery life will vary between an hour and a half and two hours.
Is this playable? For me, it isn't, but you do you.