Hi,
Snapmirror and Snapshots features are at volume level, regardless of what data protocols (iscsi or SMB). So whether you mount it iSCSI or CIFS, you will get those features.
If it's block storage then iSCSI is best the option (specially DB volumes) to present the volume. If flat files then CIFS would be good. If you create the volume with mixed filesystem type then you can share it as CIFS or NFS.
Hope that helps