That’s sort of how I do mine. I put all my data onto dropbox/onedrive. I’ve got a $100 HP USFF hooked up in my office that is a 100% online mirror for those cloud accounts, and it backs up to an 8TB external each week. I rotate that drive with a spare each month (give or take), putting the “offline” one in a firesafe. It means I have a live copy (my pc), a cloud copy (OD/DB), a second hot copy (USFF PC), a near-line backup no more than 7 days old that isn’t “live” and a cold storage copy that is no more than a month old (aka less than Apple’s deleted-pictures and Dropbox’s previous version storage time). It cost me two external drives and the mini-pc. And if all those fail I’ll probably be roaming the radioactive wasteland looking for food and losing that data won’t matter.
Oh, and that little box also runs a small FTP server and my Torrents for my Linux distro collection.