I have a 14" 1080p screen. I put everything to 125% (like font sizes, etc.) It's okay. My eyes are very good at short distances so I don't mind things being small. But yes, Windows 7 does not have enough scaling options to make higher resolutions on smaller screens work. With Windows 10 it is no problem though. With Ubuntu it also shouldn't be a problem. Yes, you do increase rendering quality, but not by much. You can still see individual pixels. But any higher pixel density probably wouldn't be useful, considering the small visual benefits and the higher CPU and GPU and thus battery demands.