Hey everyone,

As we have received no further updates to this thread, I'll now be locking it.

Please don't hesitate to open up a new thread, contact us in a support case or start a Live Chat if needing further assistance with this issue or any others. I'll also leave the workarounds suggested by @Mreclypse and @DAVEEHH below, as they helped several players in this thread previously:

Go to settings (in the game) :
Set V-Sync And Anti-Aliasing to "Adaptive"
Set game to FullScreen (Not Borderless FullScreen!)

From Mreclypse

Update driver to the newest one (I used nvidia) https://www.nvidia.com/Download/driverResults.aspx/166630/en-us
Open the game via ACValhalla_Plus directly from the game folder Go to option > Interface > General and turn off alternative hold Go to screen > Turn on vsync into adaptive and also make the game into fullscreen (not borderless)
Now start new games, and wait until the white screen then you alt tab, open the task manager and you should see that ACValhalla processes use almost 100% of cpu usage, wait until its just using 30% or so usage, then you alt tab again to the game.

From DAVEEHH

Thanks everyone!