Thanks ahoward, that's helpful.
Checking now, I see that Backblaze does not back up any of the Application support folders. I'm checking with the support but I don't expect to be able to change this. In any case, as Backblaze backs up continuously, it's likely that any backup it did make would be made when PM+ was running as that is the case almost all the time that I'm using the Mac.
My own Chronosync backups on local drives are mostly made weekly & that's too long an interval to be sure of being able to restore recent changes. In any case those backups would also generally be made with PM+ running.
I think I need a solution that would start the Mac (without starting PM+ as it is set up to do now) at night, run a backup to a local drive & shut down. I'll need to look into how I might do that.