There aren't many specific religious themes happening in the AP and the constant moving from location to location also significantly cuts down on getting too involved in local worship.
That said, Calistria is a good thematic fit because of her worship among elves and in Riddleport, but also her relationship to revenge. Revenge is the motivating factor of a ton of the NPCs and their paths to revenge often lead them down particularly bad paths through life. That said, this is a thematic fit only. I can't think of any mechanical effect worshiping Calistra would have.
