Ha! In Settings/System/Backup, if you go to "more options" you get a list of all the apps. I have both devices set to auto-backup and they backup to OneDrive.
I suppose the thing to do is to check the list of apps and see if any are missing. If any are missing, I guess need to see if there's another way to backup those.
Also, under Settings/Update & Security/Device Encryption, you can choose whether or not to encrypt the SD card... There's a warning, says if you reset phone while SD card is encrypted, its content can be lost... It's my understanding that it WILL be lost... So if anyone else tries this, I'd say unencrypt it!