4k 120hz Acer XV273K
Many people will look at game reviews or gfx card reviews and see that 4k performance in fps as low. For an apples to apples comparison, ALL in game settings are set to max, even those you don't need and are predominately post processing options used to make lower resolutions look better. Using 4k you actually turn these OFF thus freeing up processing power.
Not all games will run all settings at very high/ultra settings. So some time spent going through the settings and finding which make a visual difference with relevance to performance impact is required for each individual game, thus some fettling to get the best image quality you can @ 4k and close to 120hz/120fps. If you get a game, turn everything to ultra then you are doing it wrong, that is for 1080p and below. SOme settings like motion blur too, are switched off. Film grain, another one for me.
I still prefer 4k at lower settings at 120hz than I would 1440p @ 120hz on ultra as often, particularly for shooter games you don't have time to study the detail. Games like WItcher 3 then you want IQ above fps.
I play insurgency sandstorm, Squad and Post Scriptum as my online MP shooters and can get them all at +100-120fps (with some drops in certain busy map areas etc). I also play single player games and recently picked up Control and that game I struggle to get anywhere near 100fps and it feels like 60fps (No ingame FPS either in game or Epic launcher).
Still only running a 1080ti - the 2080ti is ~20% more perf and not worth double the money for 20% performance. I'll see what the next iteration of cards are like from both parties and price and may get a new card this gen but will wait and see, particularly on prices. The same to be said for monitors and now TV's that are 4k high hz - they are expensive.
4k was an image quality game hanger as are high refresh rates. Give me 4k (8.3M pixels) 120hz on lower settings over 1440p (3.7M pixels) 120hz on higher settings any day.
Just my view and opinion. We'll all be 4k 120hz+ with OLED quality in a few years and it'll be the norm.