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Keeping different hamster species in the same room is fine, it shouldn't be a problem at all.

Dwarf hamsters generally do better alone, if you keep a pair then you would need to have a second cage ready from the start as they can fall out at any time & fight, often they will live together ok for a while but once they mature the need for their own territory will lead to fighting or at very least dominance behaviour which can be very stressful for them.
A single dwarf ham needs a space of about 80x50cm (not sure what that is in sq inches) but a pair normally do better in a smaller space as they have less to fall out over, unfortunately that does mean you can't provide the same amount of enrichment that you would for one dwarf, you need a cage with no levels or shelves, two of everything & houses with more than one entrance for a pair.

If you've never kept dwarf hams before I would really recommend just getting one.
Most things are similar to keeping a Syrian although you will need a dwarf specific food & you need to be aware they are prone to diabetes & need a diet with no sugars, treats with honey or fruits.
A sand bath is particularly important, more so than with Syrians.