F4 fullscreens RPGMaker MV games, and works for both CS and GT. That said, keep in mind the artwork and rendering resolution for the games is fixed at 1024x768, so you're just duping pixels if you make the window bigger than that. The games are deliberately designed to be run in fairly small windows, but if you want to fullscreen them, you certainly can (and RPGMaker even preserves the aspect ratio!).