I didn't play either of the DoS games much. I put maybe a dozen hours into DoS2, and it really wasn't doing anything for me, so this will be my first experience with origin characters.
At the moment, I intend to play them all first before playing a Tav, and it's really interesting to think about what choices I'd make and how the charter would relate to the others in the party.
Dark Urge, this will be first, obviously, and I plan to play it very goodie goodie to see how that goes.
Shadowheart will be tricky because staying uninvolved is not my natural inclination. I hope the game motivates her sufficiently to get more involved. Can Shadowheart romance Lae'zel?
Astarion, what motivates him to do anything? How much of his backstory that they reveal will help motivate other choices?
Etc.
Playing a Tav after exploring the origins will be a really interesting experience, and I have zero compunction about letting my Tav psychically know everything I learn from the origin playthroughs.
If you plan on playing origins, who's interesting to you and what would you like to explore with their character?