Original Post: I have been experiencing flickering problems, however, I would not hesitate to declare it full-on studdering. It comes and goes and is difficult to WOW TBC Classic Gold figure out. It was reaching the point where it was making me insane, so I decided that I would investigate.
The short version is that it is only just recently that Windows let multiple monitors' refresh rates after almost 13 years, Microsoft seems to have tackled a long-forgotten problem when it comes to how Windows handles multi-monitor resizable rates. Windows 10's Desktop Window Manager, (DWM) resulted in frame-skips, and slowdowns when multiple monitors were running differing refresh rates. Windows 10 2004 20H1's DWM that supports the use of hardware-accelerated GPUs in WDDM 2.7 it appears to have fixed this issue , as shown by one user on Reddit.
As soon as I spotted this issue I switched from a 144hz main monitor with a secondary 60hz monitor to both my monitors operating at 144hz. The reason for this was that I didn't wish to upgrade my system and the 60hz monitor I had was due for an upgrade.
However , in doing so, I upgraded to buy TBC Classic Gold a bigger main monitor which meant that my GPU was now running lots of pixels and both at that high a rate of refresh. My GPU was now having to perform, despite being good enough for the classic WoW. It was not up to the task.