Well, in my experience 2 females can fully stock a 5 gallon. BUT, as Shell said the tank can't hold them together freely. There needs to be a divider since 2 females aren't enough for a sorority. You'll need 4 females and the minimum of the tank size is 10 gallons. So if you want 2 females, the tank needs to be divided.
For the guppies, no. They need at least a 20 Gallon IMO as they love to be in groups and they're so fast. Their bioload is pretty big as well.