Last time I looked at Premiere, it couldn’t handle the weird 47.95 frame rate that GoPros have instead of 50 (though you can halve it with 23.976FPS). GoPros own software does handle that frame rate and is actually pretty good if you’re just knocking little films together.
As others have said, higher quality settings can take a while to show on Youtube, though I’ve found they’re getting quicker at that. Mismatched frame rates in export settings is the first thing I’d check if your uploaded footage looks like poo. You want the export to either match the original frame rate or go with exactly half. In any case, if not exactly matched your output frame rate needs to be a divisor of the one you shot at.
Youtube and Vimeo only allow a maximum frame rate of 30, so if you shoot at higher rates, uploads will never look quite as good as your original footage.