Having the exact same problem (extremely slow response with everything except the viewport) after upgrading; tried to clean notifications, but there are none. Tried fresh install of Epic Launcher and UE4, absolutely the newest drivers for sure, didn’t have this issue before upgrading. Any help is much appreciated, thanks.
Asus G75VX 670MX 3GB GDDR5 18GB DDR3 3.2 Intel i7; had no issues before this