If you really wanna see their extra dialogue, I'd recommend just beelining to whatever part of the story is crucial to the origin you're playing, and skipping the hours of side quests since there doesn't seem to be anything unique for an origin vs Tav on those.
That's what I did for my Karlach run.
Was very disappointed that there wasn't some significantly better ending for her on origin.
I had been hopeful for something after being so disappointed with her endings on my other plays, but after seeing how origin kinda sucks the life out of whoever is being played I just started ignoring anything that wasn't main plot to get through it faster.
(Also extra disappointing romancing Wyll as Karlach. I thought it might be cute but he's way too slow a burn for a girl who is on fire.)
It's just weird to me how some scenes, particularly those relevant to an origin's plot, still have more attention in a Tav run.
Like when Tav talks to Gandrel, Astarion joins the cutscene and tries to steal it for himself - animated, interjecting, hes extremely present.
So it's weird to me that some of the animations didn't get kept for Astarion's origin during th at conversation. He just kinda stood there like any other convo and let narrator do the heavy lifting even tho I know he has voice lines for some of this.
I love when the character unique dialog options pop up in Origins, but they're so rare that it felt like the Karlach experience was more unique simply because it was my first run as a barbarian rather than the fact that it was Karlach specifically.
