You'd be better off with a 12600k/3080 than the power hungry and excessively overheating 9900KS. Or even a 5900x.
You'll spend more money on cooling the case and gpu and cpu than the 9900KS is worth in performance.
Bottleneck is all about balance, not performance. As resolution goes up, fps goes down, limited by the gpu. As resolution goes down, fps goes up, limited by the cpu. Doesn't matter which game, even a gpu heavy game is affected that way, or a cpu heavy game. How much fps is gained or lost is very dependent on the game.
If playing Cyberpunk 2077 and max uber ultimate settings gets you 100fps at 1080p and 40fps at 4k, you are gpu bound in both cases. Play CSGO and get 400fps/1080p and 400fps/4k, you are cpu bound in both cases.
The game will decide what balance of cpu to gpu bound you are, resolution and detail settings just make that imbalance more or less obvious.