I actually do that. I have two folders one synced up to Dropbox and another to iCloud and they are encrypted with Cryptomator. But I back up the mounted folders i.e data to tarnsap. Besides those encrypted files (fragments?) of Cryptonator were messed up by both iCloud and Dropbox over the last few years. Gratned it could be Restic and Borg (I use these two as well for larger data sets), but for very small data tarsnap has woked well for me and prices are tiny. For a larger data set, I won't pick tarsnap.

If there's an simple but "solid" GUI backup tool with (true) PAYG I'd migrate away from Tarsnap, but there isn't one.