Since my campaign isn't in the Forgotten Realms I voted for Lae'zel. While she is from a Realmspace creche, she's not from Toril and has the least ties to the planet so having her show up elsewhere in the multiverse makes sense.
I suppose Karlach and Wyll could show up too if you have a campaign set in hell, depending on which ending you get.
In BG3: Life's too short to not use the mod to have all of them in your party at all times and the other mod to make them extra chatty (using stuff from the various origin campaigns).
In a home game, Astarion, Karlach and Lae'zel are the obvious answers as the most interesting and charismatic NPCs.
I placed slightly more weight on whether I could portray these successfully as a table runner, while keeping in mind ones that I would want to meet as a player or be interested in having join my party. :3