Hopefully we get at least 10 companions...Bare minimum for a BG game. No excuse for <<6 is fine, if their are extra detailed...>> ! Pathfinder Wotr is already at 14, all pretty detailed with some great options and dialogues. I like the varied fantasy look you get versus BG3's realistic modern cosplay looking companions.
Wenduag and Lann are mutually exclusive. You can have both at various points of the game, but an early game choice will result in one of them permanently leaving the party down the road. Hence why they are both archers.
Delamere is Lich mythic path exclusive, along with several more that you can raise back to life. This is presumably to make up for the idea that the vast majority of the main companions may leave you later in the game for pursuing that mythic path.
Aivu (not listed), a baby dragon, is Azata mythic path exclusive.
Finnean is not really a companion (he is the talking weapon), but he does interject in conversations all the same.
I must say, WotR is sounding more and more interesting. I'm not a fan of gimmicks in cRPGs (like kingdom management, crusades, leading Inquisition forces, uh, pirates), but the mythic paths sound really, really cool. Few games allow you to actually become a mythical creature rather than a godly-statted humanoid. And from what I hear, those paths are very reactive.
One thing I'm curious about though - iirc paths aren't necessarily tied to alignment. (Though they do cover most alignments if you go by defaults.) So companions leaving is because they are fundamentally opposed to necromancy in any form, rather than your character's evil actions or you being locked to evil alignment because you chose the lich path? I'm not sure about Pathfinder, but in D&D liches can be good. Baelnorn, archliches.
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Regarding companion count in BG3 - 8 companions in a Baldur's Gate game is quite ridiculous. As I've said before, the ideal scenario would be 12 high-content companions (origin or not) with at least BG2 level of "richness" and another 12 companions that have less content to them (between BG1 and BG2 level) for good variety. 12 because one per class, and it divides nicely in 3 so you can have even alignment split. Of course it's completely unrealistic, it'll probably end with those 8 origins and that's it. Unless you count generic mercenaries.
I'm usually of the opinion that quality>quantity, but BG3 took it to ridiculous levels by greatly reducing companion choice, in a series that's known for good companion variety. And I'm not too certain about the "quality" of current companions anyway.