There use to be an option that automatically filled the screen (or something to that effect) but I don't see it anymore (something other than fullscreen).
Fullscreen never worked for me and currently just has the same sized window w/ a large boarder and I couldn't figure out how to use the resizable tool. I was able to reseze it but it didn't fit the screen well, was far blurier than I ever remembered and it doesn't save (when I leave I have to do it again).
Also don't know what the window scale factor or change resolution does (or how to use them)
Thanks got it to work, didn't realize I had to press fullscreen after enabling 'change resolution'.
Out of curiosity, how does the window scaling factor work? I wasn't able to change anything after clicking on it, it just slightly darkened the screen.