Going from female rats to male rats - seeking opinions (+rat tax)

My daughter has two female rats, currently just turned two years old both doing well so far. As we prepare for the next wave of rattos my kiddo wants to get boys as she understands them to be more cuddly and lazy.

My concern is how we get there. As one of the females eventually pass, I wouldn’t want to keep her alone. But I don’t know if I want to get another female for the bridge.

Can neutered males co-mingle with females? I don’t know the best path forward here with the rat situation.