[callwhendone]

I use iCloud because of Apple's Advanced Data Protection. I don't believe Dropbox offers anything like that, do they?

For backups I use Time Machine synced to a Linux home server.

[aborsy]

Not currently. End to end encryption might be an enterprise feature in the future.

If you don’t need access via web interface, you can encrypt your files using cryptomator synced to Dropbox.