I agree with KK regarding the 21:9 aspect adding to games as it gives you a wider field of view. I have the Acer Predator XR34, 34" curved 3440x1440. https://www.tftcentral.co.uk/reviews/acer_xr341ck.htm
They do a GSync version now (https://www.acer.com/ac/en/US/content/predator-model/UM.CX0AA.P01
) but I use mine in GSync compatible mode with no problem.
Oh one problem is with high res - the dots/pixels are often smaller so harder to see the desktop details as your desktop fonts are smaller too. I have to wear glasses more often than I did to read the screen.
You can change font sizes in windows options though but not ideal for some.