Hello,
after several months of using a dual-screen setup, I have noticed that I have an issue when one of the screens is turned off, and I still haven't found the problem. When both screens are on, everything works fine. When I turn off the Dell screen, there is no problem, and the screen is properly turned off in the settings. However, if I turn off the iiyama screen, which is the secondary screen, it still shows as being on in the settings. So, if I had opened a window on the screen that I have turned off and I want to have it on the primary screen, I need to turn on the screen, move the window to the primary screen, and then turn off the secondary screen.
"For example, in games, my sensitivity is modified because of this, and the mouse can wander onto the second screen when it is turned off.

Dell G2723HN (first screen)
iiyama G2530HSU (second screen)
DisplayFusion Beta 10.1 beta 3