Gohan will most likely encounter other Z - fighters like Krillin and Tien. They were all part of the group back then. Also, there's a good chance he'll meet Master Roshi. Roshi was a key figure in Goku's training, so his interaction with Gohan could be really interesting. He might also come across Bulma, who was always involved in the Dragon Ball story, either by accident or because he needs her help with some time - related technology or something.
Gohan's adaptation in the Naruto world in this fanfic would be a complex process. He would be faced with a world full of new rules, new powers, and new people. At first, he'd be confused, but his intelligence would help him. He'd study chakra, the most fundamental part of the Naruto world. He might also be intrigued by the different jutsu and try to incorporate some of the principles into his own fighting style. Socially, he'd have to learn the ways of the ninja, like their loyalty to their villages. Over time, he could become an important part of the Naruto world, using his Saiyan abilities in new and unique ways that blend with the ninja way.
In a fanfic where Gohan goes to the Naruto world, his presence would disrupt the balance. His Saiyan strength is on a different level compared to most Naruto characters. He might start by being confused about the ninja way and all the different clans. However, he could also introduce new concepts from his world. For example, his training methods. And he would probably make some really strange friends. Some ninjas might be in awe of his power, while others might be a bit scared. He could also end up having some really interesting battles against the strongest ninjas, like Naruto or Sasuke, which would be a clash of two very different power systems.
In this fanfiction, Gohan might change important events in the past. For example, he could prevent certain villains from getting stronger or save characters who died previously.
One common theme is adventure. Since Gohan has his Beast form, they might go on adventures together fighting enemies. Another theme could be romance, exploring their relationship deeper.