That's exactly what I have, but I play on 3840x1600, 24:10 Ultrawide.

I don't remember BG3 giving me any problems, even in Act 3, before the last patch, that supposedly addresses some performance problems. I loaded up a save just now and get ~50fps running around in the Lower City (very short test, only like two minutes). That's with most settings maxed and DLSS Quality.

Depending on the area, I'd probably get similar numbers in Starfield (according to the benchmarks I've seen), but for me, it's a difference playing an FPS or isometric RPG.