"I've been told the ADB backup system is not that reliable"
I have recent experience of trying to take/make full backups in order to clone company phones ( 24 of them). I can confirm that after several hours of trying many variations of ADB parameters and switches that none of them successfully managed to make a complete backup. It definitely creates backup files but it never seems to fully restore everything on the new device.
It might depend on specific needs but I certainly couldn't get ADB to make me a backup of what I wanted on an un-rooted phone. We ended up just doing everything manually, a la Production Chain...
Personally I would not trust it without having 100% managed a full backup / restore on different devices ( same model of telephone).. It might work on the exact same device on which the backup was made , but I don't know as that wasn't useful for our needs.