Replication Manager and Netbackup For Alternate Client Snaps

Hello,

I am working on snapping a VNX LUN from a Windows host, mounting the snap on a alternate host, then backup it up. I know Netbackup can handle this through EMC's VSS Provider. However, I was told that, at least for VMWare guest hosts, that we should use Replication Manager along with Netbackup to handle this backup method.

Is Replication Manager really necessary for this?

What does Replication Manager do for me that Netbackup can not?

Thanks.