The DR file can in fact be local, it doesn't have to be a NFS share. However, it is good practive to move the DR files off the machine for obvious reasons.
Volume pools are just 'logical' containers that allow tapes to be grouped to your own requirements (you can create volume pools as you need). However, Catalog tapes must be in the catalog volume pool as this is a requirement of NetBackup.
The catalog volume pool will simply contain tapes that only have catalog backups on them.