One concern I have about that is the operating system has data that's always changing unlike data like photo file storage and documents.
And assuming you ever wish to boot off that drive, for fixing or whatever, you're all set (you may need to configure the backup application for booting, that's necessary on Mac so probably on Win). A local backup to a HD is super fast so after the initial clone, which is the most time consuming (especially up to the cloud), everything else is fast.
I have a backup (clone) to a mounted backup drive that backs up every day (middle of the night). Ditto for uploading to Backblaze (the cloud). And a 3rd HD in a fireproof safe which rotates with the HD on the main system. Belt and suspenders.
You back up EVERYTHING you can't afford to lose. Or want to lose.