One possible analysis could be that it often explores the dynamic between two powerful and complex characters. Goku Black, with his menacing and somewhat twisted nature, and Vegeta, the proud Saiyan prince. In fanfics, their interactions can range from intense battles to unexpected alliances. Maybe it delves into how Vegeta would react to Goku Black's presence, given their different ideologies and power levels.
One common theme is the battle of wills. Goku Black and Vegeta are both strong - willed characters, and fanfictions often explore how they clash or come to an understanding.
Many fanfics have a plot where Goku Black challenges Vegeta's place as the second - strongest Saiyan. This leads to a series of battles and power - up moments for both characters. There could also be a plot where Goku Black infiltrates Vegeta's family life, causing chaos and forcing Vegeta to not only protect his family but also prove his worth as a fighter. And sometimes, the plot focuses on the power struggle within the Saiyan race, with Goku Black representing a new and dangerous element to Vegeta's understanding of Saiyan power.
Goku being born with SSJ4 in fanfic would likely make him a force to be reckoned with from infancy. This could result in quicker power-ups, different battles, and maybe even a shift in the balance of power among the characters.
One possible plot could be Goku from the SSJ4 form crossing over into the world of Dragon Ball GT. He could encounter new threats that require his ultimate form to defeat. Maybe he teams up with the other Z - fighters in that universe to face off against a powerful and ancient evil that was sealed away long ago and has now been unleashed.
In Dragon Ball fanfic, Goku SSJ often has super strength, like being able to lift extremely heavy objects with ease. He can also move at incredible speeds, making it hard for enemies to even see him coming. His energy blasts are much more powerful than in his normal form, capable of destroying large structures or powerful foes in one shot.
The plot might involve Goku SSJ4 teaming up with some unexpected allies in the Tournament of Power. He could be using his SSJ4 powers in creative ways, like combining them with the techniques of his new allies to gain an edge over the other universes' competitors.
Bulma could be involved. Since she has a relationship with Vegeta and is friends with Goku, she might try to mediate between them when Goku snaps at Vegeta. She could be the voice of reason, trying to calm both of them down and make them see each other's point of view.
One possible storyline could be that Naruto is somehow transported to Goku Black's universe. There, he has to face Goku Black who sees him as an intruder. Naruto would have to quickly learn about Goku Black's powers and find a way to fight back using his ninja skills. Another storyline could be that a powerful villain creates a rift between their two universes and pits them against each other. They start off as enemies but then realize they are being manipulated and team up to fight the real villain.
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.