APP Download small versions of files in sync folder

I want to use the desktop app to have a folder with all the files in the cloud.
Is it possible to just load the full file when its needed? The whole purpose of my cloud is, besides making all files available on all systems, to free up some space. If I always have the full size files in the sync folder, I don’t reach that goal.

I thought about using samba for this but I had some problems that I could not always connect to the server.