I admit I'm a bit dubious towards how the Origins stuff is going to pan out in the full game.
A lot of the Origin character content seems like it's built from the assumption that the player is playing a different character, so what happens if we are playing as one of those origins characters, do they...not trigger? If you are playing as Gale, can you invite Wyll over and play the 'Weave' scene from Gale's perspective? If you are playing as Shadowheart will there be a scene where you start hearing voices in your head and stumble into camp to confront Asterion/whoever and his party? If you are playing as Lae'zel and get to the part where people are starting to turn, do you have the option to pull a knife on one of your companions and get talked down by them? We know some of these character-defining scenes are going to be in (like the Aserion feeding one), but I really am doubtful that all of them will be.
One thing that I'm keeping my eye on is the romance paths, in that I am pretty skeptical that we'll be seeing the other side of them from the perspective of their respective Origins characters. For one, there is no 'Tav' romance-if you romance an origins character, you get their romance dialogues, and their romance scenes. It's written to be very player initiated, but each romance being unique to the character you are romancing. I'm not getting the feeling that if you are playing as Shadowheart for instance you'll see wyll teasing you about not being able to swim, or be given an option to ask Lae'zel if she wants to hold hands by the river instead of dominating you. You'll be following Wyll or Lae'zel's romance path, not Shadowheart's.
So I'm thinking that playing as the Origin's party members is going to come with some big tradeoffs in terms of content vs having them as companions. At the same time, I'm aware that even if a lot of their companion-content probably isn't going to translate over when we are playing as them, it's still looking like they are going to have more complete storylines and rp options than good 'ol Tav. Like I have very little expectation that playing as a custom Githyanki is going to have as much unique content as playing as Lae'zel, or that the custom Warlock PC content is going to hold a candle to Wyll's storyline with Mizora. No wizard PC is going to feel as wizard-y as Gale, etc, because Tav was written much more generically to fit all of he roles, but it comes at a noticeable cost. Maybe Larian will surprise us with a storyline unique to the custom PC that you don't see as an origins character, but even if that comes to pass I'm expecting much less reactivity from the story to custom PCs in regards to class and race at least.