All fine so far. You could also forego NFS and mount directly from Nextcloud over SFTP:
You can also then mount it as a user on the remote system with write access, and not worry about NFS style permission mananagement:
So again, create the groups you need, assign the users to the groups, then limit the shares by group:
/data is typically user root, so all users will get access to the normal /data/ directory by default. Differentiate how you mount shares if going the NFS route so it doesn’t look confusing in 6 months when you come to troubleshoot:
/data = default NC storage
/media/nfs_share1 = first share
/media/nfs_share2 = second share
/media/nfs_share3 = third share
/media is just an example. Mount it wherever you feel comfortable but do so out of the webroot (/var/www... ) for security.