i have a 3 gallon shrimp tank with at one point 10 shrimp in it. cherrys are smaller and tend to live loner but are more expensive than ghost shrimp. small shrimps wont add much to the bio load but bigger shrimp deff do. fish the size of crayfish will poop as much as a common pleco IMPE.
small shrimp in a 2 gallon is good considering you have good filtration and a steady temp. as for food...about once a week ill throw something that sinks to the bottom. theyll clean it up and also feed off small organisms that live on live plants.
my shrimp tank has 6 white clouds in it and when i feed them, they get whats left over.