Exactly. Yep. You're on a roll, that's exactly what would happen.

The main advantage of the online backup, besides that it's easy, would be that you could conceivably access the files in a pure Windows system if you really, really needed to get at them. You'd need to install something like 7zip to extract the tarball, and it'd take a long time, but you could do it.

Except it doesn't look quite so easy now since your system can't understand XFS. You'd have to reformat the drive as something else, or install XFS drivers. It's possible you already have them, just haven't loaded them yet -- try modprobe xfs. (The offline backup doesn't care what's on the USB drive -- it overwrites it all raw.) I like bare-metal backups. Having an entire working installation to throw in when things go seriously pear-shaped has let me stumble through a few awful mistakes learning experiences mostly unscathed. It's neither quick, pretty, nor elegant, but it's powerful. Harder to do for a complicated system, but yours only has one disk.

You could even keep the backup "fresh" in a similar way to the online backup, once you have it, since almost nothing but user files are going to change.