Here's my two cents on Gale. I definitely think he's being on some level manipulative. There are just moments when his manner and approach feel... less than genuine. Moments when it feels like his interactions with us are especially considered and curated to get the reaction he wants. I also think that he's still holding something back about the whole Mystra/orb situation. I don't think he's lied about anything he's told us, but I think there's still some details that have yet to be revealed that maybe paint him in a less than charming light. That having been said, I still think he's ultimately trustworthy. I think that any manipulation he's engaging in is ultimately in service to dealing with the orb, an existential threat that could kill not just him but everyone for miles around. Which I think is fair and reasonable. The threat it poses is big enough that I'm not going to fault him for putting a bit of extra effort into ensuring he has help dealing with it.
So yeah that's my thought on Gale: Manipulative? A little bit, non-maliciously so.
Astarion meanwhile? Definitely not trustworthy, will very likely betray us if it benefits him.
Shadowheart? I think she'd be willing to betray us as well, though less likely than Astarion. Astarion I feel would betray us for a broad scope of reasons while SH is more focused on her mission so unless her mission calls for it, we're probably fine.
Wyll? I think he'd betray us too, if he doesn't undergo character development. I think at this point in Act1, he could betray us if the situation was dire enough and he felt desperate enough, though he'd definitely feel bad about it. I think Wyll definitely wants to be a good person and with support he can be. You see it in his interaction with the tieflings. He doesn't have to help them at all, they clearly don't have much to offer him in pursuit of his goals. Yet he's there anyway. His goals aren't purely selfless, but they aren't purely selfish either. I get the sense that in all his time as blade of frontiers, he wasn't afforded the opportunity to really build close, intimate bonds of trust, since he had to keep being a Warlock under wraps. Which means that Mizora, the cambion who's goal is to corrupt him is the only intimate relationship he has, the only person who knows all about him and who he can open up to, which can't lead to anything good. Having other people know his secret and thus, allow him to open up to them could be exactly what he needs.
Lae'Zel? I don't think she'd betray us in the sense that for betrayal to happen that implies deception at play. From the beginning she lays out her priorities crystal clearly. She's incredibly trustworthy in the sense that if you listen to her at all, then it won't come as a surprise if she tries to kill you, you'll probably be able to figure out why pretty quickly.
