A fanfiction could explore Gohan's Ultra Instinct in a training scenario. He could be training with Piccolo or Vegeta, and they are both amazed and a bit envious of his ability. Gohan then uses his Ultra Instinct to help them understand new ways of fighting and power - up techniques. This would strengthen their bonds as comrades and also make them more formidable as a team in future battles.
In a 'Gohan Raised by Vegeta' fanfiction, Gohan's personality would likely change a great deal. Vegeta being his mentor would mean a strict and no - nonsense upbringing. Gohan would probably be more confident in his Saiyan heritage. His fighting style could be a blend of Vegeta's elegance in combat and his own natural potential. Also, the relationship between Gohan and other characters like Piccolo or Chi - Chi would be very different. With Vegeta's influence, he might be more rebellious against Chi - Chi's wishes for him to focus on academics.
There are many good writers out there. Some popular ones might be those who have been in the fanfiction community for a long time and have a lot of positive reviews. However, it's hard to name just a few as new talented writers are emerging all the time.
The Ultra Beast could completely change the direction of Ash's journey. It might introduce him to new regions or dimensions he has never explored before. For example, if the Ultra Beast has the ability to open portals, Ash could end up in places with new Pokémon species to discover and new challenges to overcome.