I also find it to be very slow on many networks, and even in ideal conditions it might get 2MB/s when the phone has a 10MB/s connection.
For photos and predictable stuff I thus use syncthing, and the odd very large thing I send using scp with termux.



This. Aegis does all of the points except offsite backups. And for good reason.
The Aegis app has no network permissions at all, which is obviously a massive boost for security and privacy. And besides, off-device backuping is a nightmare.
Syncing the Aegis backups made on change to some other server is better handled by a great dedicated app. Syncthing is the best such program (by far), though for the few files involved here nextcloud would work just as well.