Ok this is a bit of a weird one.
The following applies to window 10 (maybe linux too but I don't know).
I have a project that runs fine on a machine with a Nvidia dedicated GPU. But when I run on a Intel NUC (with Intel integrated graphics) the contents of the window are scaled up mostly in the vertical direction up from the bottom left (I think). Also the mouse cursor position doesn't match up. So it would seem that the rendered output is getting scaled but the input is not. When in boarderless mode this goes away. This seems to happen with both Opengl and ANGLE.
I haven't filed a bug yet as I'm not 100% sure whats happening here.