I can't really point to one specific fanfiction as there are so many out there. But you can start by looking at popular fanfiction websites and filtering for Dragon Ball Z, Krillin, and Android 18. Check the reviews and ratings to find a good one.
In some fanfictions, the focus might be on how Android 18's android nature affects their relationship. For instance, there could be a story where Krillin has to deal with Android 18 having a malfunction that makes her act differently. He then has to find a way to fix her without losing the essence of who she is, and this creates a lot of emotional and action - filled moments in the fanfiction.
Android 16 was created by Dr. Gero. His origin story involves being designed as a powerful android with a peaceful nature. He was made to be a part of Dr. Gero's plan against Goku and the Z - fighters. Android 16 has a unique appearance and is very strong, but he doesn't have the same malicious intent as some of the other androids.
Goku is often paired with Android 21. Their relationship can be explored in different ways. Maybe Goku wants to test his strength against her, or they could end up training together to face a common enemy.
One interesting storyline could be Android 21's struggle to find her true identity. In fanfiction, she might discover that she has a hidden past or purpose that was not initially known in the original series.
The origin of Android 16 in Dragon Ball Super is quite fascinating. He was created by Dr. Gero, who was hell - bent on getting revenge on Goku. Android 16 was crafted with great power and unique abilities. However, his personality is different from what one might expect from an android created for combat. He has a love for nature, often seen observing birds and enjoying the outdoors. This is in contrast to his main purpose of being a combat android. His origin story also includes his relationship with other androids. While some were more aggressive, he had a more subdued and peaceful nature, which makes his story in the context of the Dragon Ball Super universe all the more interesting.
Yes, there are. For example, some fanfictions might explore Krillin's character in new and unique ways, like giving him new powers or putting him in different situations within the Dragon Ball universe.
Gula was a character in Dragon Ball Super. He was Flisa's older brother and had higher strength and potential than Flisa. Gula appeared in the movie version and Dragon Ball Hero, and showed his powerful combat ability. His form was more advanced than Flisa's, and he had even forced the Super Saiyan into a desperate situation. Gula's strength and potential were obviously higher than Fliesa's, but he disdained to compete with Fliesa for the throne, so he did not become the emperor of the universe. Although Gula appeared in the movie version, his strength and character status made him included in the official history of Dragon Ball. All in all, Gula was a powerful character with potential, and he had a complicated relationship with Flisa.