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.
Well, it could be about Gohan achieving some great power-up that makes Vegeta jealous. Maybe Gohan saves the day in a big way while Vegeta fails, which could be seen as 'Vegeta sucks' in the context of this fanfic. As for the 'lemon' part, perhaps there could be some hinted romantic tension between Gohan and another character, but in a very mild, non - explicit way.
One thing that makes it unique is the non - traditional pairing. Vegeta and Gohan don't have a typical relationship in the original Dragon Ball series. So in the lemon fanfiction, it's an opportunity to explore a whole new dynamic between them, which can be really interesting for those who like to see different character interactions.
One possible plot twist could be that Gohan becomes more powerful than Vegeta much earlier than expected. This would create an interesting dynamic as Vegeta would have to deal with his student surpassing him. Another could be that Gohan discovers a new Saiyan ability that Vegeta was unaware of, which could change their relationship and how they approach training.