Weird FPS Cap Issue

I am running a dual monitor system on Windows 11. When I start WoW on my main screen it doesn't always get the highest priority. That results in a 120 FPS cap, instead of the usual 190 FPS. This happens when I have a task on the other monitor active, like Firefox or Discord. Now here comes the twist: It would not be a problem if it was sufficient to click on the mainscreen to grab priority and start the game, because sometimes I even get 120 FPS when I do just that. And when I close the game, then all of a sudden Firefox or Discord shows highest priority again. Once I get WoW to start with maxpriority and 190 FPS, I can do something on the other screen, like opening more Firefox windows, and it doesn't change. Once WoW has highest priority it keeps it, but getting there is the issue. Now what I can I do to assure that starting WoW puts everything else that I am running on the system at a lower priority?

https://imgur.com/a/trtPMPt

This is the problem on a screenshot: https://imgur.com/a/trtPMPt

That hidden main task seems to happen when I move a Firefox window to the second screen. Apparently it stays hidden on the main screen and grabs priority. It could be an issue with Firefox, but it's not 100% clear. Maybe it's Windows. Maybe there is a way to get around all of this. That's basically what I am asking for.

/console maxfpsbk -1

Interesting! Gonna try it out.

Nope, doesn't fix this particular problem which seems to be taskbar-related. It was helpful nevertheless.

Following up on your idea I also modified Firefox about:config layout.frame_rate from -1 to 0. Let's see how that works out.

Ok, scratch that. While it may solve the issue it makes Firefox too slow.