I found this answer when i googled for flickering, slow performance, and crashes. In my case it was related to G-sync being on in the nvidia control panel under “set up G-sync”. I had it set to ON, and ENABLE FOR WINDOWED AND FULL SCREEN. This caused the issue.
Specs:
Mobo: X470 AORUS ULTRA GAMING
GFX: Nvidia Gtx970
CPU: AMD ryzen 7 1700
RAM: 16384MB