To be honest, I'm curious about Gale. Do I understand correctly that romantic Gale wants to take the crown anyway, and friendly Gale wants/needs to depending on some factors? In my case, friendly Gale himself said he would give up the crown, and there was no option to convince him or suggest he take the crown for himself. He decided his quest on his own without any influence from my side. I wonder, of course, what that depends on.
At the end of Act2 and beginning of Act 3, when finding out about the Crown, Gale is interested in it as a problem solving tool. In the romanced version, after finding the Annals of Karsus, he takes the PC aside (the boat ride) and talks about how he could take the Crown to put the power of the gods into mortal hands for the betterment of the world. You then have a discussion about what to do. In it your PC can roughly hold four positions: that power corrupts; that Gale is wonderful as he is and does not need the Crown; then you can allow him to sweep you of your feet with his plan; and finally you can edge him on. Afterwards you are invited to the audience with Mystra, where he will again search your council in how to proceed. If your choice here drastically conflicts with your previous conversation, he will remark on it and behave like you originally discussed. I really love how his quest is constructed because it feels like you are doing something with the character.
The boat ride has no ability checks, it is pure conversation so it matters what you say, and each version of the conversation has a lovely flow and once you picked a mood - so to speak - you can stick with it, if you like. That is to say, if you edged him on, you still have the option to regret you decision later, but also have ample dialogue to simply stay on board with the plan. On the other hand, if you persuaded him away from the Crown, he will understand questions about taking the Crown as checking in on whether he still feels good about the decision the two of you made. I haven't explored the dialogue when you take the third option yet, when he is undecided til the last.
I overall think they did a very good job with this quest and I wish Astarion's had a little of its reactivity. There are quite a few points indicating that the ritual is as much a crutch to Astarion as the Crown is to Gale. But, along with the conversations you can have about the other spawn, all your conversations about these topics amount to nothing during the final moments before the ritual. They are just fluff without relevance and I think that is a lost opportunity.
Edit: I just wanted to add, that while I love Astarion, I also occasionally want to strangle him or at least thunderwave him of a cliff into a camp of gnolls along with Shart and Wyll. But alas, evocation wizardry prevents such measures, so I have to pet him with one hand, while using the spray-bottle with the other.
