I can't address the breeding issues. I just know that you can't keep two together permanently....we had two girls at once and they fought.

I prefer wire cages, because I think the airflow is better, and there is more climbing space. But I don't use wire cages any longer due to a couple of mishaps with interested dogs (the hamsters were ok, by the way, but it was scary), and plastic and wire cages are easier for the hamsters to escape from. Olivia lives in a glass aquarium, well out of the reach of the dogs and cats, but with plenty of ventilation. Just make sure you get plenty of toys to keep the hamsters active. They like to exercise....all night! Our little Evelyn met an early demise last summer while in a glass aquarium.......I had it too low, and the dogs tipped her over while we were away. I learned a valuable lesson.