About adding cat fish to my tank?

ive got a tank big enough for clown loaches, guppys,mollys,platys,rummy nose tetras in shoals, neon tetra in shoals, but what i want to ask is can i add little catfish like corydoras or dwarf corys or something like that. if they dont mix ill just get some plecos, also ive been hearing about a type of cichlid you can mix with these fish!! is this true??