automating backups

[tdalej]

I am to the stage setting up automated backups of an opnsense installation.
I see the API documentation, and that looks like possibly the answer, however ...

Is the entire configuration stored in a single file as in the backup from the UI?

I have used another, similar product that contained the configuration in a single file and a very simple korn shell script was all that was required to obtain a copy of the file that could be used for restoration.

/conf/config.xml seems to have a majority of the config -- can it be used to restore on a fresh install?
If so, what is the advantage of the APIs for backup?