I just tried this out via a German email and cloud service called Mailbox and it's solid.
Address book and calendar configuration + sync are super quick and smooth; none of the address book formatting oddities or calendar glitches I've experienced in Nextcloud. File sync was equally fast and no fuss.
Web GUI has a bit of a corporate feel but it's clean with a good amount of white space.
The Mac and iOS apps work well but there's no Dropbox-like Smartsync "Local vs Online only" feature for the Mac. It has a form of selective sync but it wasn't behaving like I'm used to in Dropbox (turning off a folder still left the folder on my Mac? Maybe a bug).
Couldn't test 2FA without using my own domain.
All and all quite impressed.