I'm not entirely sure specifically what a 'beerus raps beerus fanfic' is about without more context. It could potentially be a fan - created story where the character Beerus is rapping. Maybe it involves Beerus expressing his thoughts, his powers, or his experiences in the form of rap within the context of a fan - made fictional narrative.
There could be a storyline where Beerus, out of boredom, decides to train Goku Black instead of fighting him. But Goku Black misinterprets this as a sign of weakness and attacks Beerus. This could lead to a battle where Beerus has to hold back at first to avoid killing Goku Black, but as the fight progresses, he realizes he has to use his full power to subdue him.
In fanfiction, it's really hard to say for sure. Different fanfictions might have different outcomes. Some might make Goku Black super powerful and give him the win, while others would keep Beerus as the dominant force due to his status as a God of Destruction.
You could try looking on fan - fiction websites like Archive of Our Own or FanFiction.net. They usually have a wide variety of fan - created works, and there's a good chance you might find a 'beerus raps beerus fanfic' there.
Beerus would likely be more powerful. He is a god of destruction in his own universe with incredible cosmic powers. Naruto is extremely powerful in his world, but his power is mostly based on chakra and ninjutsu, which is on a much smaller scale compared to Beerus' ability to destroy planets with a flick of his finger.
Frieza might initially be shocked. He's used to being a feared and powerful being, and the idea of having a family is very foreign to him. So he could be in denial at first.
Well, Naruto could be in awe of Beerus' power. Maybe he tries to learn some of Beerus' combat techniques. Since Naruto is known for his determination, he might pester Beerus to train him.
With King Kai, Beerus as a girl could have a different kind of relationship. She might be more patient with him. King Kai might be a bit more nervous around her at first, but then they could develop a more comical and friendly rapport, with Beerus teasing him in a more light - hearted way.
For Yamcha, you can focus on his growth from being a bit of a comical character to a more serious and respected fighter in the context of his relationship with Frieza. Maybe he learns from Frieza's cold and calculating nature how to better strategize in battles. For Frieza, his development could be about him learning to care for someone other than himself. He could start to see Yamcha as an equal, which is a huge shift from his usual superiority complex.