The only sure solution to your problem is to simply delete the app, and then reinstall it before you next need to use it. Once you log back it it remembers your flight stats and stuff, so all the cached stuff you’re concerned about will just go away.
Leaving it several days does seem to remove any residue that may get left behind when you instantly reinstall it.
As for panoramas, go to https://exiffixer.com/ from your phone and upload the flat version from your photo album to get the exif data back so you can straight upload it to facebook/kuula as a 3D image from your phone if that’s what you want to do. I believe choosing Ricoh Theta S as the camera model in the conversion is what people generally recommend, I’m sure someone else will correct me.
On a computer the best application I’ve used is Kolor AutoPano. There’s a really good workflow here: 360 Panos using DNGs
THe software is discontinued, but can be ‘obtained’ if you’re stuck, give me a message.
When you transfer videos to the app from quick transfer I think they are still compressed, so the only way to get the proper high quality file is via the SD.
As Steve suggests don’t get too hung up on it if you want the best pictures and footage you’ll always going to have to transfer from the SD to a computer. You can then use other methods to get those pictures from your computer to your phone if you want them in iCloud. (I’m lucky I have a QNAP NAS with phone apps, so I can easily move photos from my network attached storage device to my photo roll in a few taps. EDIT: I just brought a MacBook Pro so now it’s even easier! 
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If you’re only doing Social media stuff, then you can probably get away with the app versions.