I meant aspect ratio, in the sense that the reason why I couldn't get good scaling behaviour in the first place is because none of the scaling options in Godot seemed to work satisfactorily when stretching the window into both a widescreen-y shape and a more mobile-y portrait shape. But deciding not to try so hard to support mobile, and instead having a fixed aspect ratio, would free me up to use more sensible scaling options.
Might need to make a separate export for mobile with different settings. I dunno, I'm bad at dynamic UI layout.