Don’t think you can do that - causes issues. Dropbox has pretty good redundancy in itself. I think you can recover most stuff up to 30 days. They’ll have backups of backups.
For me, I backup my home server using Duplicati. It backs up to an internal hard drive on the server itself (so, not redundant to loss, but would be quickest to recover from) and also offsite to BackBlaze - which is FAR cheaper than say, Amazon.
Using Duplicati, has the benefit of compressing your backup to encrypted packets rather than a 1-1 mirror, so it is more secure in storage, as well as quicker to upload. Can also be set to have multiple versions backed up and you can recover files individually. It also means you can set it to only backup changes rather than your entire hard drive each time.