Lae'zel redemption arc starts after the creche. If you agree to
spoiler
enter the astral prism either after or before fighting the inquisitor
You don't need to do the zaith'isk, but imo it's nice to get the story context of what it actually does. If you do, you need to roll a few saving throws and if you fail there's some extremely bad permanent debuffs which can only be cured by eating a space gummy, so if you're absolutely avoiding using those you might want to steer away. If you succeed all of them you get a significant buff to your illithid powers, if that's something that matters to you. If you let Lae'zel do it instead, it's much harder to avoid getting the penalties.
If you decide to fight the creche, please save the egg and take care of it
Is it true that you can see colors and stuff in the milky way if you're somewhere without light pollution? That seems so cool, I wish I could do that, but I'm also too cowardly to travel to somewhere completely dark at night.