When you say online FPS, can you give some examples? Fortnite and stuff like that?Really can't decide what monitor to go for when I get my pc running a 4090 a 4k 144hz or 2k 240hz mainly playing online fps.
I might suggest an Ultrawide then, you see enemies coming into view earlier, plus less resolution to drive than 4k so better framerates.Cod at the moment and any future online games eg new division multi player etc