GPU will never bottleneck a CPU.
(Kind of) Detailed Explanation:
In a game, CPU produces random things (pedestrian, bot movements) and GPU visualizes them. No matter how hard a CPU works, you can't see the results if there are no graphics cards to visualize it, so what matters is the GPU. The weaker the GPU, the weaker the power a CPU needs to balance them. The performance and the CPU usage will go down, but it won't be as bad as a CPU bottlenecking the GPU.
Proof:
Integrated Graphics. Do you know how weak an iGPU of the 6700K is even compared to an R7 250? A fair amount. But an iGPU can still play games and get almost the same results as mathematically measured, without any "bottlenecking".