The Avengers' reactions would vary greatly. Natasha Romanoff might see it as an interesting study of human creativity. She'd be looking for any hidden motives or messages in the fanfiction. Bruce Banner would be intrigued by the different takes on Doctor Strange's powers. He might even start thinking about how some of those fictional concepts could be applied in a more scientific context, if possible. Clint Barton would probably just laugh it off and say it's a fun way to pass the time.
The younger characters in Encanto like Antonio would be excited. He loves stories and new ideas, so Mirabel fanfiction would be like a new adventure for him. He might want to share it with his animal friends. And Dolores, with her ability to hear everything, might already know about the fanfiction. She could be either intrigued or a bit worried depending on how the fanfiction is being received by the rest of the village. If it's causing a stir, she might be concerned about the family's reputation, but if it's positive, she would likely be quietly supportive.
Sure, Doctor Strange has been part of the Avengers in the comic universe. His magical expertise added a unique dimension to the team's capabilities and strategies.
I wouldn't say Doctor Strange comics are niche. They offer unique storylines and magical elements that attract a specific group of fans. But they haven't achieved the same level of mass popularity as the most well-known comic franchises.
Doctor Strange's fate in the comics can be quite complex. Sometimes he seems to die but returns through various plot devices or magical means. It really depends on the specific comic arc and creative direction.