https://www.neowin.net/news/microsoft-amd-nvidia-are-all-sleeping-on-windows-11-mpo-display-issues/
 
While there are plenty of bugs and issues on both Windows 10 and 11, one of the most recurring problems that plague user PCs is related to MPO or Multiplane Overlay. The feature was introduced by Microsoft in Windows 8.1 via Windows Display Driver Module (WDDM) 1.3. When executing multiple frame buffers, MPO was meant to reduce CPU and GPU overhead with the help of a fixed-function hardware unit in the display controller as opposed to using up shader cycles.
However, the feature has often been plagued with issues. And although Microsoft has in the past dealt with problems and bugs related to MPO and other Desktop Window Manager (DWM) features, in recent times with Windows 11, the issue seems to have mostly been ignored by hardware vendors like AMD and Nvidia, as well as software giant Microsoft.
Plenty of forum posts and threads online are from users who fixed seemingly their display issues by disabling MPO. In fact, Nvidia had once issued a hotfix that recommended disabling the option via a registry tweak. The classic symptoms generally include stuttering, black screen or white screen issues, flickering, among others, in Windows, as well as in browsers like Chrome or Edge. It is possible that some enterprise software display issues, like the one where the Citrix workspace mouse cursor goes white, could also be fixed. Some users say driver timeout issues were fixed too.
 
While not every display-related bug is due to MPO, disabling the option could come in handy if you have been unable to resolve the issue by other means. To disable MPO, head over to the Display Window Manager (DWM) registry address below and add the "OverlayTestMode" DWORD value 00000005.

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\Dwm
"OverlayTestMode"=dword:00000005
 

1. Go to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\Dwm
2.  Right-click > New > DWORD 32-bit value
3. Name the new DWORD value "OverlayTestMode"
4.  Modify OverlayTestMode DWORD value by right-clicking
5. Enter value data "00000005"

To restore MPO in case you encounter any issues after this, simply delete the OverlayTestMode DWORD you created. However, if internet voices are to be believed, then disabling the feature certainly seems to magically cure a lot of the problems out there.
 
Good software advice for those who have these issues. 

(excerpt)
The classic symptoms generally include stuttering, black screen or white screen issues, flickering, among others, in Windows, as well as in browsers like Chrome or Edge.
(end excerpt)
 
sigh, more buggy Windows & drivers issues
 
As MPO started way back with W8.1 (meant to reduce CPU and GPU overhead) --> new hardware has so much more performance ... why is it even on by default in W11?

too busy trying to push everyone's systems into a 'free' upgrade to Win 11 , instead of fix a small problem