The impact on the fandoms is multi - faceted. In the case of the Harry Potter fandom, it can introduce new storylines and character developments that were not possible within the original series. Fans get to see how Harry would react in a completely different universe filled with superheroes. For the Avengers fandom, it adds a touch of the magical and the complex backstories of the Harry Potter world. This can attract new fans to both fandoms. It also encourages creativity as fans try to blend the different powers, cultures, and ethics of the two universes in their own works.
The main differences are in their expressions and some minor details of personality. In the manga, Deku might seem a bit more intense, while in the anime, he's sometimes presented a bit softer.
One popular 'Overwatch Reacts' fanfiction could be the ones where the Overwatch characters react to different timelines or alternate universes. For example, they might react to a world where the Omnic Crisis was never resolved. Another could be their reactions to new heroes joining the team. It's all about exploring the characters' personalities through these reaction scenarios.
Well, obviously Deku in two forms - the younger and the older version are the main characters. The younger Deku is the one who is still growing and learning, while the older Deku has more experience.
Another plot might involve the older Deku being from an alternate timeline. He shows the younger Deku different ways he could have developed his skills and relationships, which makes the younger Deku reevaluate his own path as a hero.
As of now, Deku is very much alive in the manga. The plot hasn't reached a point where he meets such a fate. Usually, main characters like Deku have significant story arcs and aren't easily killed off.
Well, usually they focus a lot on the Doctor's reactions and emotions to various situations. The fanfictions might also explore how his character develops in unexpected ways.
Naruto's outgoing and boisterous personality would make Deku more confident. He would probably be more upfront and less shy. Naruto's strong sense of justice would also intensify Deku's already existing desire to help others.
Bakugou could use his words. He might tell Deku that he believes in him. For example, he could say 'Deku, you may be a nerd but you're a strong nerd.' It's a backhanded compliment but it shows he has faith in Deku.