It depends on the resolution. Everything from WQHD is handled by the GPU, in FHD depending on the game. But realistically, what games do we have? We had CSGO, which became pretty GPU-cast with CSGO2, and then you have the popular eSports titles Valo, Dota, Fortnite.

But you're everywhere on levels where nobody actually plays. Who still plays in 720p today? :D

The CPU is perfectly fine for a 7900XTX.

It all depends on the game and the monitor…

But, usually using a x3d CPU helps a lot. I gained a substantial fps boost from upgrading from a 5900x to a 5800x3d