Goku is, without a doubt, one of the most popular. His constant pursuit of strength and his ability to overcome seemingly impossible odds make him a favorite for fanfiction writers. They can create all kinds of new adventures for him, like facing off against cosmic threats even greater than what he's encountered in the shows.
Obviously, Female Cell herself is a very popular character in these fanfictions. She is often the center of the story, with her own unique take on the Cell character. Another popular character is Gohan. Since he has a connection to Cell in the original series, in the fanfictions, he often has interesting interactions with Female Cell, whether it's a friendship, a rivalry or something more. Bulma also pops up a lot. Her intelligence and resources make her a great addition to the story, especially when she's interacting with Female Cell, perhaps trying to figure out the science behind her existence.
Pan is often a popular character in female Saiyan fanfiction. Since she has Saiyan blood, writers like to explore her potential as a powerful Saiyan female. They might give her new powers or have her go on adventures that were not shown in the original series.
Future Trunks is often a central character. His time - traveling aspect gives a lot of scope for interesting plotlines in 'Dragon Ball Z Legends Fanfiction'.
There are no such inappropriate 'Straight Shota' stories in the official Dragon Ball Z canon. Dragon Ball Z mainly focuses on epic battles, power-ups, and the adventures of Goku and his friends to protect the Earth from various villains.
One alternative is to focus on character backstories. You could write about the early days of Piccolo, how he came to be the way he is. Another option is to do crossovers with other non - sexual universes. Maybe a story where the Dragon Ball Z characters meet characters from a magical anime world and they have to work together to solve a problem. Also, you can write about the relationships between the characters in a platonic way, like the deepening of the friendship between Gohan and Krillin.
A Kryptonian in the Dragon Ball Z universe could potentially be a very powerful addition. Their natural abilities like super strength, flight, and heat vision could make them a force to be reckoned with. However, they would also face challenges as the Dragon Ball Z world has its own power scale with ki-based powers. They might have to adapt to the different fighting styles and power sources. Maybe they could learn to use ki in addition to their Kryptonian powers, or they could find a way to combine the two in unique ways.
Dragon Ball Z is both anime and manga. The anime was adapted from the manga and they share the same story and characters, but presented in different mediums.