I had aphyosemion primigenium killies in a planted 6 gallon Eclipse. I had 4 adult fish and they had lots of babies. Graham at Noah's Pet Ark told me that they would do well in a smaller tank and they sure did. They were quite interesting fish. I never tried them with shrimp.

I have chili rasboras/ boraras brigittae and they are quite pretty. For sure, they'd be happy in a small tank. They're tiny. They are fine with shrimp.