it depends really on the species, i would not expect cardinals and rummy noses to stick together however neons and cardinals that look similar would
if they look similar in terms of size and colouring then they will probably shoal together
the othe thing to consider is the species, for example with Bronze Cories and Albino Cories, these are the same species but different colour morphs so will shoal together (but it would be better to get a group of each or just choose one of them)
so if they look the same, or are the same species then yes they will, otherwise no they won't.