This review by steamdeckHQ has a full section on Deck performance.

TL;DR (AI summary):

Surprisingly playable on the Steam Deck at a mostly stable 30 FPS. However, this comes with significant visual compromises, including dynamic resolution leading to pixelation and blurriness, noticeable ghosting, frequent model pop-ins, and framerate drops in towns. The game also suffers from high battery drain and occasional model glitches. While a significantly better experience is expected on more powerful hardware, the game is still enjoyable on the Steam Deck, albeit with these limitations.