I ike that you recognise a problem with the larger rainbows. You might want to remove them and return them to the store. They probably won't give you anything for them, except, (maybe), a credit.
Some fish schoool esier than others, especially with the confusion of all the opther fish in your community, even in the tetra family.
Neons are pretty nice and they school well, though they're hard to keep in numbers unless you give them perfect conditions. I'm hoping tp get a neon tetra school of at least 20 soon.
I'll think about other small schooling fish later as I'm tired right now.