In my 25 I have about 10 astraea, 4 scarlet hermits (2 in the sump), 3 nassarius
In my 10 I have 3 hermits, 2 astraea, 2 trochus.
The banded really isnt a CUC-its more ornamental.
Youre good on hermits-dont want to overdo those lol make sure you have bigger shells than they have tossed in there too or they will go after snails. For the most part, they are meat eaters, they dont graze much. I tend to overfeed, thats why I have them. ps-scarlets are the *most* reef safe, and some people will never have hermits for a CUC because of the meat eater fact.
If you have a lot of algae, astraea are the way to go. You could do 5-8 of them.
If you have sand I would suggest getting 1 nassarius too. They stir up the sand a good bit but they are meat eaters (extra food)

I like nass. because they look like zombies coming out of the sand at feeding time hahaha
With that said, your CUC really depends on how much algae (and a little bit on what type) you have. if you dont have much, your CUC will die.