New 360Hz QHD monitor, really sluggish behaviour when alt-tabbing

I have a Philips Evnia 27M2M8500 360Hz OLED running in landscape and LG 27GL83A-B 144Hz running in portrait, both displays QHD. When I turn on the computer, alt-tab from a fullscreen application, etc. it can take like 20-30 seconds and the computer becomes completely unresponsive during this - can't hear Discord or any audio sources until it recovers.

I have tried messing with HAGS, 'Optimised settings for windowed games', and disabling fullscreen optimisations in the properties of the game EXE.

Searching around, I've found this thread. Sounds like I have to deal with it, but at the same time it sounds like people are only suffering with 2-3 seconds, which I was accustomed to. The monitor does utilise DSC, which is apparently the culprit, but it shouldn't be taking 20+ seconds.

Any help is greatly appreciated during this time!

Merry Christmas

Make sure to install the newest version of GPU driver.