For a start you might not have a choice on which kind of dwarf you get. Any dwarf hamster you get in any pet shop is going to be a hybrid between the Russian Campbells Dwarf and the Winter White. That's how similar they are! The only way to get a pure RCD or WW ham is to find a breeder who breeds pedigree hamsters and depending on where you are geographically you might not have access to that. Finding a breeder is also a great way to find a hamster that is well used to humans and handling so I think that's your best shot. If you give a general idea of where you are in the world someone might be able to help you find a breeder local to you
If you can't find one that's okay! A hybrid ham is a wonderful little animal though they do need some special care. They are prone to developing diabetes as a result of being hybridised so they need a dwarf hamster specific diet and can't really have any high sugar treats regularly. Even then you need to be on the lookout for signs of diabetes like increased urination.
There's no difference between the space you need for a dwarf and a syrian though, dwarfs are extremely active and (this is purely a personal opinion and others will differ) 400 square inches isnt a great amount of space. Not going to focus on that but I will recommend you look at the "show us your cages" threads in the Housing subforum to see what kind of setups are common.
No hamsters should smell really if you do regular spot cleans, they are very easily potty trained so it's easy as pie to keep their cages fresh with small cleans and just change the bedding once every month or so. Sometimes a syrian female will have a musky smell when she's on heat every 4 days or so but not all do and I don't know if dwarf females smell as strongly. Personalities are all different and calmness and confidence depends a lot more on how a hamster is raised than its species or sex but in general males seem to be calmer.