That’s pretty normal, when full screen is on, your computer will have to render more pixels, therefore causing FPS to drop (lag). You can probably get a similar result to using windowed mode by going into “vibrant visuals options” at the bottom of video settings, and turn the resolution scale to something like 66%, which basically runs it in a window and scales it up to full screen. It will make it look a lot worse but should reduce lag.
MeeemBeem
That’s pretty normal, when full screen is on, your computer will have to render more pixels, therefore causing FPS to drop (lag). You can probably get a similar result to using windowed mode by going into “vibrant visuals options” at the bottom of video settings, and turn the resolution scale to something like 66%, which basically runs it in a window and scales it up to full screen. It will make it look a lot worse but should reduce lag.