With Astarion I didn't have issues and I romanced him in a patch 3 playthrough with early high approval as a Durge.
Although I never got an option for Shadowheart even tho I got her approval really high. I must've missed the chance somehow. Everyone else seemed doable, but never tried Karlach or Wyll.
Shadowheart has one line: I think, we should get to know each other better. That triggers here wine scene. But if you start anything with anyone else, that line isn't there anymore.
I found out, because I was undecided,whom to romance with my gith mage, if she would fit with Shadowheart or Gale or someone else.
I had that line with Shadowheart, until I accidentally started the romance with Karlach and decided to go with it