The Red Wizards were also a core part of Dungeon and Dragons Online's last expansion in Myth Drannor. While forgotten, since it was released in the heyday of 3.5 Edition (the last good edition of D&D), DDO is still going and getting new content.

Obviously to my mind, the Dark Urge is the intended protagonist. The original series was about the Bhaalspawns, and he is basically the core of the entire plot. I expect the canon version will be a white dragonborn storm sorcerer.

Of the group:

Shadowheart, Gale, and Laezel are core to the events of the game; the Gith, Sharran cult's actions, and Gale's affliction having direct, tangible impact on the events in game. Regardless of who you pick or anything else, you will cross their respective narrative arcs somewhere at some point. I believe a canon party, if they stuck to the 4 limited in game, would be these three with the Urge.

Astarion, Karlach, and Wyll seem more side characters than directly involved. Astarion's entire arc is a side quest, as is Karlach's. Wyll's arc only comes into indirect with the main plot by happenstance of family, not really majorly involved like the core three above.

Minthara is of course a late Act 2 addition, basically there because you lose out on a front liner if you side with the cultists in Act 1. Entertaining, but a side character. Halsin as well, with his arc finished in Act 2, about the time you actually get to recruit him. Jaheria and Misc are legacy characters without a real arc or reason to be there, outside of linking to the original games, and are very late additions to the party.

Which kinda brings up a minor complaint. You're missing a recruitable Bard, Sorcerer, and Monk entirely, while the only recruitable Druids, Ranger, and Paladin are well along in the game.

It's a minor complaint, and understandable as creating entire new arcs and voicing lines for a half-dozen more characters would have been expensive and time consuming. Also a complaint I have with BG1.