Access USB drive shared from one RPi from another RPi?

I have a 2-drive level 1 RAID running on a dedicated RasPi 3. I'd like to access the content in said RAID from another Banana Pi which is running as a Plex server. I can access the RAID NAS from my Macs in the house to load the content, but when I edit my fstab on the Banana Pi, do I treat the RAID as an EXT4 drive (that's how the drives are formatted)? Do I use Appletalk? (it's running netatalk to talk to the Macs)... Do I need to install NFS or is that redundant/unnecessary? Is CIFS involved? The mount command and fstab entry will somehow need to incorporate the login and password for the RPi RAID NAS computer.