4k doesn't actually exist. 1080p is 1920x1080. 4k is 3840x2160. So in realistic terms it'd be 2160p.
720p is HD. 1080p is Full HD (FHD). 1440p is QHD (Quad HD) and 4k is UHD (Ultra HD).
They call 1440p as 2k because it's resolution is 2560x1440, it's not really close to 2k, but that's what's it's called. 4k is the same thing, 3840x2160, which is 4x the resolution of FHD.
2k and 4k are just common usage terms, not actually technically correct, but close enough for advertising purposes. The general public would see 2160p as double 1080p, when in reality that's just vertical, not horizontal as well.
But those are standard 16:9 widescreen resolutions that'd you'd find commonplace anywhere. What are gaining in popularity are the Ultra (21:9) and Super (32:9) widescreens, which aren't any taller than a 16:9 monitor but are 1.5-2x wider, a Superwide is basically 2x monitors side-by-side without the bars in the middle. Awesome for some games like CSGO or Battlefield or CoD as you'll get a massive field of view side to side.
Most of the Superwide will play standard 16:9 or super 21:9 by boxing the screen, so you could youtube and game on the same screen, like picture-in-picture.
A 3090Ti would not be overkill by any means on a Super or Ultrawide 1440p because instead of 2560x1440 you'd be pushing 5120x1440 or 3440x1440.