I would try the Flume 2 app (I have not used it for video but does a nice job with photos and it does do video — I give them higher resolution shots and they do a nice job of getting it into Instagram). But Instagram is not very high resolution regardless. Considering what its for and how much $$$$$$$ they have, its kinda WHAT? Google drive has much better resolution and processing but they are not set up well for social media. They expect people to be collaborating with your media. What world are they living in. This isn’t Hollywood. The collaboration happens during production not usually in post at the editing stage. At least give the option for people to download but not change what is posted.
Imacs (i7), Canon C300, Canon 5D Mark IV, Panasonic ENG HPX250P, , FCP X, teach video production in L.A., Cool Light Productions, Producing series of multimedia Portraits of creative women in the production arts.