It really depends on the perspective. Elena is often seen as the good girl, the one with a pure heart. She represents the moral compass in many fanfictions. But Katherine has this allure of mystery and a long history of survival. If you like characters with depth and a darker side, Katherine might be better in the fanfiction world. However, if you prefer the more traditional heroines, Elena would be the top choice.
The main distinction of porn with a story genre from regular porn is the presence of a coherent narrative. Regular porn often jumps straight to the sexual action, while the story genre tries to add some kind of story framework around it. But in the end, both are adult-oriented and feature explicit sexual content.
Well, it's hard to say for sure. The concept of 'porn-like' is quite subjective. Some might consider certain novels with excessive sexual descriptions as such, but it depends on individual perspectives and cultural standards.
In many places, 18+ porn comics are considered illegal. This is because they can have a negative impact on society and violate moral and legal standards.
One great 'Katherine Pierce Fanfiction' is 'The Redemption of Katherine'. It shows a different side of her character, exploring her past traumas and how they shaped her into the complex vampire we know. It has an engaging plot that keeps you hooked from start to finish.