For the first question, only one character has path that allows the player to pick between bimbo and muscle growth. I thought about it for other characters but that would end up doubling the amount of writing and rendering required as well as complicating some of the planned later story beats, so I decided on having each character follow a single transformation path that made the most sense for their story. I did try to have an equal balance of bimbos and muscle girls, though.
For the second question, there aren't any plans for femboy style characters at the moment.