Whenever I play any game, I have the game itself playing on M1, and everything else on M2, Chrome, Discord, various Steam windows, windows task manager, etc.
Everytime I launch BFG, it forces Chrome to go windowed, moves it to M1 and stretches it to fit the screen. Discord is also moved from M2 to M1 and stretched to max.
It also minimizes Winamp and Windows task manager, and moves the Steam friends window to the middle of M2.
This all happens after the opening credits finish and as soon as the main menu loads.
When I close the game, Winamp pops back up and the Steam friends window moves back to the right edge of monitor 2, but Discord and Chrome remain stretched to max on M1.
After the main menu loads, I can alt+tab and move everything back to where I want them, and they will stay there.
All in all, it's not a big deal, it's just kind of a nuisance.
The game itself is great though! I love killing heretics and xenos in space boats!