sync iMac local files with Dropbox vs Sierra iCloud sync

[oakrrl]

I'd love to use Sierra's sync features which keep local and iCloud versions aligned while also monitoring free space. BUT iCloud just isn't reliable enough (see Ben Lovejoy's right-on comment today on 9to5 Mac).

So I pay for a 1 TB Dropbox account., trying to keep files on my iMac and MacBook coordinated. My setup is old iMac as main machine with 1TB drive, (hopefully new iMac with 2 TB fusion drive soon, if Apple ever upgrades its iMac so it has a usb-c connection) and a 500 GB SSD on 12" MacBook for travel.

It would be easy if I just kept all my files in Dropbox and accessed them from each machine. Why have any local copies at all to keep track of?

But in that case - where's the backup of my Dropbox files? I don't want to rely totally on Dropbox, and want the security of a physical local copy (preferably a physical copy plus a physical backup).

Is there some way of keeping all these in sync? i.e. the files in Dropbox, the local files on iMac and MacBook, and a physical backup?

Any help much appreciated. Sorry if I'm covering old ground. Seems this should be a common issue, but I can't seem to find information on a search.

Thanks!