Fullscreen and Monitors

Alt-tab minimises the game, the mouse cannot reach your other screen, or fullscreen is the wrong size.

Display
You wantSetting
Instant alt-tab with no black flashBorderless Fullscreen: fills the screen as a window instead of exclusive fullscreen.
The game to stay fullscreen when you click your other monitorKeep Fullscreen on Focus Loss
The mouse to leave the game while a menu is openFree Cursor in Menus
Every launch fullscreenLauncher, Settings, Default fullscreen; or Launch fullscreen on one profile.
A specific window sizeLauncher, Settings, Resolution.
F11 switches fullscreen in game.