It depends how you define 'dwarf hamster'. Some people define it as belonging to the Phodopus genus, and therefore there has come to be the view that only Campbell's, Winter Whites and Roborovskis are dwarf hamsters (I think this may have arisen from legislation in certain American states where hamsters of the Phodopus genus are legal along with Syrian hamsters, but those not of it, i.e. Chinese hamsters, are not legal.)
I do class Chinese hamsters as dwarf hamsters as this is not my view; I show them in the dwarf section of shows, I judge them as a dwarf hamster judge and their standards are in the dwarf section of the NHC handbook
You're welcome to your view, but it's all down to your definition.
I've found Campbell's easiest to keep in pairs/groups, with Winter Whites next easy (though more prone to squeaking). Robos have a tendency to seem OK and then attack each other silently. Chinese are the trickiest, and I rehome Chinese individually as pets as it's not nice to wake up to the result of a falling out of two Chinese hamsters.
If you buy a pair/group of dwarf hamsters you need to have enough cages, room and resources to house each member of that group in their own cage.