Ultrawide is generally 2560x 1080.....which is a bit more than your "regular" 1080p.......which is 1920 x 1080.
I run a GTX 1080 for regular 1920 x 1080 and it's plenty.
I came across this....
"I got the LG 34GL750-B on Prime day. Roughly the same specs as yours (2560x1080, 144hz). I'm currently running a GTX 1080 and for the most part any game that I'd want at a higher framerate (shooters, in other words) I can get there. Might have to tweak settings a bit on some brand new stuff, maybe. "