I found that linked article full of misinformation and opinion. I suggest forgetting it. Looks like clickbait anyway.
These three are the common approaches to backup: Time Machine, an online backup service like CrashPlan, and a separate hard drive or other machine that you own. I use all three: I use Time Machine for backups of DEVONthink databases without problems. I also back up all my computers to CrashPlan and I’ve had no trouble restoring data from there, either. And you can always backup your databases to a network hard drive if you want. In fact I have several local backup destinations on my local network. Altogether I backup to five different locations. There is no need to be so compulsive, but I worked hard to get these data and don’t want lose any of it.
For a full backup, you’ll want to locate the databases in your file system (their extension is .dtBase2) and copy the whole thing to your backup destination.
If you index files on an cloud drive, those files are not stored inside your database – they remain on GoogleDrive or wherever. The database contains metadata about those indexed files – thinks like their location, their tags, the place in the database where the file is indexed, and a concordance of the words in those files which is used for See Also and Classify and some other features. It’s a good idea to backup your database in order to get a backup of these metadata, but if your database got destroyed for some reason your files would remain safely where they are on GoogleDrive etc.
I feel it’s always a good idea to have a backup for cloud storage somewhere else than other than that cloud – you can decide what to do about that, or not.
There are dozens of other threads in the forum on different backup protocols that other users follow. Or read Bill DeVille’s posting on backup here. Definitely read the Joe Kissell book that Bill mentions in his article.