The Bnha universe's reaction would be mixed. Those who are into complex stories, like Todoroki, might study the relationships in Hamilton fanfiction. But others, like Mineta, might not be interested at all because it doesn't have much to do with his usual interests. Overall, it would depend on the individual characters' personalities and interests.
Some would be inspired. Characters like All Might might see Peter Parker's journey as similar to his own in some ways. Both are trying to do good in a world full of challenges. All Might could appreciate Peter's determination to protect his city despite having a normal life outside of being a hero.
For heroic - centric fanfictions, they would likely be disdainful. Since they oppose heroes, seeing stories that glorify heroes would annoy them. They might scoff at the idealized versions of heroes in those fanfictions.
Typically, the decisions about who lives, who dies, and who tells the story in an animatic are made by the team of writers and animators. They consider various factors such as character arcs, the overall theme, and the intended impact on the audience.
Some characters in bnha scary stories are unique to those stories. These new characters are often created to add to the spooky or suspenseful atmosphere. They might have really strange or terrifying quirks that we don't see in the main series. For instance, a character with a quirk that allows them to manipulate shadows into terrifying shapes that can attack people. So, in many ways, they are different from the characters in the main series.
Yes, the Bnha manga has finished. The final chapters wrapped up the plotlines and brought closure to the series. It's been quite an adventure for fans.