I have had mollies in a 10, by themselves. They have a huge bioload, the regulars get between 4-6 inches big, and they are brackish water fish. I do not suggest them, as they are also prone to mouth fungus, and other diseases more than any other fish I've dealt with. Although they are nice, they are also aggressive, and should be 1 maleto 3 females. Balloon mollies, are smaller generally getting maybe 2.5 if that, because of the deformity that is now a breed... They are not as aggressive, should still be 1 male to 3 females, and they are harmless for biting. Their mouths were made more for algae eating than fish attacking
I've had them too. I prefered them in the 20, because they grew and flourished better.
That's my opinion on experience =D
although platys are a good choice, I am bad with stocking 10s which is why they contain only ever guppies (gender divided) or betta fishies :3