I have a similar problem, I believe (can't see your video for some reason), except that it always happens on 1080p or lower (monitor has native 1080p), not just while gaming. Also, in games, shadows are often grainy instead of soft. I found this thread on reddit (https://www.reddit.com/r/AMDHelp/comments/s178kz/grainy_shadowstextures_6900xt/) and someone posted a fix, quote:
"[...] Basically open AMD adrenaline, go to: Settings->display->Enable virtual super resolution. Then you go to ingame settings, fullscreen mode and set up a resolution higher than your native. for instance 2560x1440 if your screen is 1920x1080.
It worked wonders for me, the grainyness is gone!" (KhaineKhaine_ on reddit)
This also works for my second monitor by setting the resolution in Windows above the native resolution of my monitor (>1080p) but it's a suboptimal fix because sharpness is lost and everything looks kinda mushy. I am thinking of RMAing because of this. Very annoying.
