Question Bottleneck

There is no such thing as "bottlenecking"
If, by that, you mean that upgrading a cpu or graphics card can
somehow lower your performance or FPS.
A better term might be limiting factor.
That is where adding more cpu or gpu becomes increasingly
less effective.

Some games like sims, mmo and strategy games tend to be cpu limited.
Fast action games tend to be graphics limited.

Do you have a 8600K and are looking to upgrade to a GTX1080ti?
If so, run this test:

Run YOUR games, but lower your resolution and eye candy.
If your FPS increases, it indicates that your cpu is strong enough to drive a better graphics configuration.
If your FPS stays the same, you are likely more cpu limited.

I suspect you have identified a good combination of cpu and gpu.