Dropbox and hard drive space, Mac

I have always wanted Dropbox files to be online on all devices so I have not fiddled with that setting.

But now I briefly tried other options: it is possible to right-click an item in a Dropbox folder and make it online-only (Finder lists and Get Info continue to display the old size, but there appears a "cloud" icon and Get Info says "zero bytes on disk" until I actually open that item).

Maybe this explains more (the preference setting I mentioned in my previous post still seems confusing and does not seem to work as expected -- maybe it needs to be turned ON/OFF or other fiddling...):

https://help.dropbox.com/sync/make-files-online-only

edit: Maybe this would do it:

Check this Dropbox setting. Contact Dropbox support for details.

The bigger the contents of your Dropbox is, the more space it will reserve on your Mac should you need to sync your files. Basically while dropbox stores your files online, it also keeps a smaller version offline. And so if you have 30GB worth of files offline, it will have around 1-3GB of your local storage taken for those smaller versions of the original files.

For me, I have about 45GB of files on iCloud Drive, and it takes up about 4.67GB on my local storage.