In the manga, Krillin doesn't stop training. His sense of duty and the need to protect his comrades push him to keep improving his skills and strength.
Maybe a story where 18 and Krillin decide to open a martial arts school. They have to deal with different types of students, and it shows their relationship growing as they work towards a common goal. It can include how Krillin uses his knowledge and 18 her strength to train the students.
Well, Vegeta would be a likely character. He might be initially suspicious of the female Goku. Maybe he thinks she's a threat or just can't believe there's another Goku - like being. He could be there to add some comical moments as he tries to understand the situation.
Their relationship can be explored by showing how they support each other in daily life. For example, Krillin could be shown helping 18 with her android - related issues, like dealing with any glitches or upgrades. And 18 could be there for Krillin when he has self - doubt about his martial arts skills.
A really interesting fanfic idea could be set in a post - apocalyptic version of the Dragon Ball universe. Android 18 and Krillin have to fight to protect the few remaining survivors. They use their unique skills, with Android 18's android powers and Krillin's martial arts. Their relationship becomes a source of hope for those around them, as they prove that love can still exist even in the harshest of times.
In general, it's a bit of a toss-up. The strength of Manga Goku and Anime Goku can vary depending on the specific arcs and battles. Sometimes, it might seem like one is stronger in a particular situation, but that could change in another.
In some fanfictions, Krillin might time travel to the era of the Saiyans' first arrival on Earth. He could then try to change the outcome of the battle, perhaps by warning Goku earlier or finding a way to defeat the Saiyans with his own skills and wits. This would be a really exciting story as it would completely change the course of the Dragon Ball universe.
The dynamic between 17 and Krillin in the fanfic could be a mentor - mentee type of relationship in some aspects. Even though 17 is an android, Krillin has more life experience and knowledge of the martial arts world. He could teach 17 some of the subtleties of martial arts and strategy. Meanwhile, 17 could show Krillin some of the unique capabilities of his android body. This exchange of knowledge and skills would create a strong bond between them as they team up for various adventures.