Question cpu bottleneck?


Feb 23, 2019
So this is my pc specs=
Asus PRIME Z370-P motherboard.
i5 8600k cpu.
gtx 1070 ti gpu.
32 gb ddr4 3200mhz ram.
2 ssd disks and 1 hdd.

I have fps drops in most of games that i play . a few games however works fine (GTA V. elder scrolls online. path of exile. wow. etc.)
I read on the internet that the GPU usage should be 100% which it isnt for me mostly. maybe in Rust it is something like 80-90%
but usually it can also be below 50% especially in GTA V the gpu usage is very low or not at all (maybe a reading error?)
My cpu however is all the time around 60-69% while playing games
so i wonder might it be my CPU is bottlenecking? also The i5 8600k should be good enough for my gtx 1070 ti. but since i get
drops in so many games something must be wrong. I do not get blue screens or crash in games. also my PC status says that its healthy.
i ve tried alot of things as well but they havnt solved the problem. recently also i ve experienced my OS freezing (windows 10.) which
causes the mouse to lag. this happens sometimes when im loading a program or a game. Can this also point to that its the PSU? and how do i check if its the PSU?
Would be glad for help.