Frame drop on full screen

Hello, so I’ve been building a landscape for a little bit now. I get 30 - 40 fps while windowed, and 25 - 30 fps on fullscreen. The scene is composed of several speed trees (2500 - 3000 tris, with 500 - 700 tris on LOD) and grass foliages (600 tris per clump with 100 tris on LOD.) I don’t really know why this happens or how to fix it. any ideas?

I want an explanation as well; I’ve observed that this happens in most programs on fullscreen but not on borderless window (fullscreen)…

I’ve heard it has something to do with texture streaming but not from a very reliable source.

When playing in fullscreen the res goes up ti the maximum res of your screen, lets say its 1920x1080 but in the editor the window may be just 800x600 res