For now I did not have to restore any files but what happens if all my drives fail? I install duplicacy and then add the storage and it will detect my previous backups or what I should do? Is there any duplicacy config that I should backup or something?
You shall save credentials to access storage, and any encryption keys if you have backup encryption enabled.
Password manager that replicates everywhere is a good place for that.
I would recommend going through the exercise of restoring a few files on a completely new machine (or new user account on the same machine) at least once, precisely to make sure you maintain access to all the keys and secrets.
Must the config file be available in order to restore? I.e. should I back up the config file?
did you manage to find an answer to this?
Yes, this config file is necessary for restoring any backups. However, the decision to keep a copy of this file depends on how much you trust your storage. If you think there is a chance that this file may get damaged or lost, then simply backing up this file alone is not sufficient. You’ll need to set up a secondary storage and use the copy command to make a copy of your primary storage.