I go home and my laptop is smart syncing the recently active sessions only which conserves space on the laptop drive but lets me do some small work on recently active sessions.
It's totally seamless and I cannot recall the last time I was even alerted by Dropbox about anything except that I was hitting my 3TB cap soon.
The only issue I ever had was using it on Windows where it would occasionally create conflicted file copies, which was annoying, but moving to OSX resolved that.
I use Nextcloud and there are parts of the UI that defy logic. For example, when I select a file it brings up an "Actions" menu that's hidden via a hamburger button. It has 4 options and I have about 3000px of horizontal whitespace on the same row.
TLDR; It's all hamburgers and whitespace and I don't understand why.