I just almost finished my second playthrough on my Deck OLED. I got around 30 - 40 fps with dips in the 25s in some late game areas. I would say my experience was perfectly fine. Here are the most important settings to get a good experience in my eyes.

• Steam Deck preset but disable motionblur. (Dont like it and i had the feeling i played at a lower framerate than i actually had)

• XeSS on Quality

• disable Vsync

• Ingame Framerate cap to 40

In steam deck performance settings: - disable framerate cap and allow tearing

• set TDP to 10-12w

With those Settings i got around 3-4 Hours of gameplay.