"X CPU can/can't handle X GPU" is misleading and not exactly true. The CPU acts as a varying FPS in different games. This cap can change throughout the game, however will not be reduced by decreasing resolution and most settings (excluding View distance, possible shadows, and physics). This FPS should be the same no matter the graphics card in play. I'd say an i7 7700 is good for <100FPS in modern AAA titles.
The GPU is more in charge of the resolution and graphics quality settings. For modern AAA games, I'd suggest 1080p at 60hz/FPS. It really depends on the game though, refer here: http://www.techspot.com/review/1393-radeon-rx-580-vs-geforce-gtx-1060/
Which games are you looking to play?