Gorochu:
Fun fact, don't panic if you lose weight at some point, you are going to lose muscle mass.
May your transition goes as smooth as the curves you'll grow!
That actually depends on how active you are while you gain.
You can gain both muscle and fat at the same time. You can also maintain it as well. Body composition is truly fascinating.
While you don't need to get buff, I do recommend all feedees and gainers to have at least enough muscle to lug yourself around.
Also, cardio is important for heart health - something to keep in mind as you grow.
