Resolved the screen flashing issue. Stupid Teamviewer!!! I installed BF4, similar issue in full screen. Decided to uninstall stuff and after removing Teamviewer, the flashing was gone. Now, I had Teamviewer on my old system but when I reinstalled it, in the Advance settings, there an option to ignore alpha blending. I need to have this checked(which is was not) for the flashing to not occur. Now, BF1 will still only select medium setting in Auto. Hopefully, will get the EVGA FTW3 next week and if it performs better, I'll RMA the Gigabyte Xtreme(either get a refund or replacement card which I'll sell). Ugh! Will still try and figure out why I'm getting poor performance.
My psu is a Corsair 750w something. It's been a while since I built a new system, will play more when I have time.