The build is purposed only for extreme gaming. The 2600x will have an overkill CPU cooler.
That all depends on the game and graphical settings. There is not a blanket answer to this. Bottlenecking all depends on the game and graphical settings and any CPU can bottleneck any GPU under the right circumstances. Bottlenecking is not a absolute thing or a yes or no thing like it is made out to be.
Also it is 100% meaningless to even think about provided you chose your parts right and get what you want. You should chose the CPU for the FPS you want and the GPU(s) for the graphical performance you want. If you are happy with what you get and meet your goals then why worry about something that is not impacting you?
Farther info: https://pcpartpicker.com/forums/topic/214851-on-cpugpu-bottlenecking-in-games
I have come to the conclusion You need to right up all the questions you always answer and they should just be pinned to the top of all the forums.
Sure even a 8700K overclocked to 5.3ghz can bottleneck a GTX 1080 depending on the circumstances.
But does it matter?
Any card can be bottlenecked by any CPU it is all a matter of what is being run.
You should always double check benchmarks in your uses to ensure any part choice will meet your needs, if it doesn't then no matter what you do you are limited by that part.
Except for getting a bit lower fps than with an i5-8600K or i7-8700K, everything else depends from the GPU.
And you should play at least at high settings with that GPU.
Relative performance (at 1080p) between an Ryzen 2600X and a i7-8700K (both stock) is ~9%
You are more likely to bottleneck a GPU at this point in time before a modern processor tbh. (given 1600/2600 and above as well as 8400 and above for intel) for games.
For streaming/recording while playing, it can be bottlenecked but it ultimately depends how heavy you are into multi-applications, if you are considering this route you should probably consider a 2700x over the 2600x.