In the complete Heatwave: Sam's Stay you'll guide Sam through the first few days after he moves in with Michael in this new town. So it's a story experience with choices, the gameplay for the full game is about 3-5 hours.
In this first game Sam is still coming to terms with his sexuality so other guys lead the way a bit more (Sam leans a bit more bottom, though you still often get the choice to top or bottom)
In future games and near the end of this one, as Sam gets more confidence he also becomes a bit more dominant.
Hopefully that answers your questions! Feel free to ask anything else!