I love my skunk cleaner shrimps , always out and about and clean my hands when they are in the tank. I’ve had just about every other one but they have been a little more reclusive. As you can see by my avatar, I’m a big fan of my tuxedo urchin by far the best cuc in my tank, nothing mows down algae like it. I have micro brittle stars but might not be your thing as you only see their little arms sticking out of the rocks. My go to for hermits are the dwarf red and blue legged hermits. They have never bothered a snail ( I do keep plenty of empty shells scattered around). You might like the Halloween hermit, very cool looking, but they only use conch shells and may be risky for your current and future conch. Other than the snails you mentioned, other good snails are turbos, trochus, ninja stars and ceriths. If I had a choice between a serpent star or a brittle star, I would choose the brittle star.