This is good, but it needs some work.
I think it would be easier if we could also import existing rclone.conf files. But I think your implementation of the encryption is custom, right? You aren’t using rclone itself (?). I tried creating a crypt remote, but because the app doesn’t ask you for all the same info as rclone, I wasn’t able to get it to work. Specifically, I use rclone on a crypted GDrive that is also using the app folder. Because I wasn’t able to provide my own Google Drive credentials, I wasn’t able to access the app data folder.
The app doesn’t work for me because of that, but this is a good step towards having rclone on iOS. I think the biggest roadblocks for iOS devs is implementing all the ChaCha20 suite as there aren’t any existing libraries for it (that I am aware of). If you got that going, that’s a very good first step.