After syncing the nextcloud app to my Surface Pro, the folders/files that are on my nextcloud server filled the local hard drive and rightfully could not finish the sync. Why if nextcloud is a sync does it download ALL of the files to your local hdd? Does this situation sound like there is something I clicked or didn’t click to cause this?
I have nextcloud set up in docker on an unraid server.
Open the Nextcloud app and make sure that you’ve only selected to sync the files you want to see on your device and not all. That should reduce tha amount of required hard disk space 
The next cloud desktop app did not “SYNC”. It literally downloaded the entirety of folders to the surface pro. There must be something I clicked to turn that on. I searched the interwebs extensively to see if anyone else had this issue and came up dry.