I can confirm, even trying several different combos of optimizer mods, plus running the resolution at 1280x720, it stutters like crazy as soon as you get out of the initial area surrounding the Imperial City and looks like dogshit because of everything at low or lowest.

Baldur’s Gate 3 with almost 100 mods (including optimizers), and similar upscaling settings at 1920x1080 in Desktop mode, runs better on the Steam Deck.

Since the remaster is literally using the same game logic as the original, I ended up just installing the GOG version of the GOTY edition, installed a bunch of mods, and it runs amazing. I don’t think I’m missing much in the way of changes/improvements.