basically, a princess fills the duelist role (and/or MR tank/lightning rod), so only a valk can really be close, although bandits can potentially take on this role with their high hp pool.
in any case, a collection event for a princess should be coming to us soon (claudia) so best to just prep your SCs for her.
and no, I don't think there is any combination that is more effective than just putting a princess. in fact, most guide videos won't use princesses unless absolutely necessary.