I've always set the rcopy groups to match the VVs being added, CPG wise, I'm sure I've seen an error when one didn't match but been a while (might just be the user CPG). The remote/target CPG settings I think were added to support the automatic creation of target VVs with the VMware plugins (the settings didn't exist before that from what I remember).
We've not had tiers in a 3PAR for 5+ years so had little need to mix CPGs and we don't have snaps around for long so wasn't a priority where they were stored.
Sorry you might need to experiment unless someone else has mixed settings and can share.