Sync files from smb share

I have an unraid NAS hosting a nextcloud docker that I am syncing several home computers to. With multiple users on each home computer, the disk space becomes limited.
I have a NAS share that I can share over the lan with SMB. I would like to have each user use that share as their nextcloud share, while only accessing the folders they should have access to. (although this second part is not required)

My question is, if I have a SMB shared dir that was once synced with my current nextcloud dirs, but is not quite up to date, then I specify that as the sync directory on a new nextcloud install, will nextcloud sync correctly? I am afraid of deleting my files.

I looked into external storage options in nextcloud, but I don’t think that covers my use case.

Is it as simple as mounting the smb share, then using that as my nextcloud sync folder for each user? Or is external storage or something else what I need?