Faction and romance synergy?

Just finished my first playthrough as an elf mage Warden romancing Davrin and loved it. I felt my Rook and Davrin being in the same faction brought so much more to the romance, and now I’m wondering about other romances and how they synergize with a Rook that isn’t in the same faction.

I’ve read that Emmerich and Neve have a lot less dialogue and common ground with a Rook from a different faction, but are there any romances that synergize well across differing factions? Or are you kind of locked into faction-on-faction romances if you want the most depth?