The Archer router does have a means to backup and restore its configuration but it may not be available on the models from TPG.
Logon to router and go to Advanced > System Tools page..
Is there an option Backup & Restore?
You can backup the config to a file on your device.
And then restore the config if you have to reset.
VOIP will only work on a router from TPG, not a 3rd party one.