Steam Deck Optimized Settings
This one's simple: to get a 30 FPS experience with an occasional drop to the high 20s, set FSR to Balanced and drop everything to Low. You can increase textures and Anisotropic Filtering to Medium or High. Just watch the latter because it can slash the average frame rate a frame or two—not much when playing the game on a beefy PC, but enough to mess up the 30 FPS experience on the Deck.
The performance in Midgard is much better, but if you want to have a playable experience in Svartalfheim, you'll have to apply the aforementioned settings combo. You could also set FSR to Performance or Ultra Performance for an even stabler 30 FPS experience, but the image quality takes too big a hit for us to recommend this route. If you decide to lock the frame rate, use the in-game frame limiter instead of the built-in one since that one noticeably increases latency.
No, FSR frame generation does not feel great at low frame rates, so we recommend avoiding it on both the Deck and the Ally.
The game will squeeze every watt out of Deck's TDP, so do not expect the battery to last longer than about an hour and a half on the LCD version or about two hours on the Steam Deck OLED.