DB Heroes doesn't follow the manga exactly. It takes inspiration and builds on it, making changes to suit the specific requirements of the series. However, the core elements are still recognizable.
Vegeta is also very likely to be a hero in the new story. He has grown a lot throughout the Dragon Ball series and in DB Legends, he might play a crucial role in fighting new threats. His Saiyan pride and his determination to surpass Goku could drive the story forward in interesting ways.
One aspect of Vegito and Female Gogeta fanfiction could be the exploration of their unique power combinations. In these fanfictions, writers might create scenarios where they team up against a powerful enemy. For example, they could face a new, extremely strong villain that neither could defeat alone. Their combined strength and different fighting styles would make for an exciting story.
The length of DB mangas differs. It depends on factors like the story's complexity and the author's vision. Some might run for just a few volumes, while others could have dozens.
One common theme is the power dynamic. Since Gogeta is very powerful, female characters in the fanfiction might either be in awe of his power or strive to match it. For example, a female Saiyan could train hard to be as strong as Gogeta.
Another theme is the exploration of power. Since Gogeta is extremely powerful, in these fanfics, the female character might either be in awe of his power or strive to match it. For example, some fanfics show the female character training hard to reach Gogeta's level of strength.