His appearance would likely change. He could have paler skin, redder eyes perhaps. And his senses would be heightened. He would be able to smell blood from a distance, hear the faintest of sounds. Also, his speed would increase. He could move like a blur, which would be a huge advantage in many situations, like escaping from danger or chasing after someone or something.
In a fanfic where Harry gets turned into a vampire, one thing that could occur is that he would be shunned by the wizarding community at first. They would see him as a threat. But he could also use his vampire powers to his advantage in fighting the dark forces. He might be able to use his enhanced senses to detect danger earlier. Also, his immortality could change his perspective on life and his long - term goals. He could become more isolated as he outlives his friends, or he could try to find a way to reverse the transformation.
Well, he might struggle with his newfound thirst for blood. He'd have to deal with the wizarding world's reaction, which would probably be a mix of fear and fascination. His friends might be torn between helping him and being scared of him.
Another challenge would be his changed appearance. His fangs and pale complexion could make it difficult for him to blend in at Hogwarts. He might be ostracized by some students and even some teachers. His vampiric abilities, while useful in some ways, could also be a hindrance as he tries to maintain his normal wizard life. For instance, his sensitivity to sunlight could limit his outdoor activities during the day.
One interesting fanfic could be 'The Vampire Potter'. In this, Harry's transformation into a vampire brings a whole new dynamic to the wizarding world. His vampiric abilities, like enhanced speed and strength, make him a formidable force against the Dark Arts. He also has to deal with the prejudice from some wizards who fear his new nature.
Well, in the fanfic, Harry as a girl might have a different experience with the sorting hat. Instead of being sorted into Gryffindor easily like before, the sorting hat could consider her new personality traits due to the gender change. She might even end up in a different house, which would completely change her Hogwarts experience. And her interactions with the other houses' students would be very different too.
As a girl, Harry might be more cautious in some situations. In the original story, Harry was often quite bold and impulsive. But now, she might think twice before jumping into dangerous situations. Also, her relationships will shape her differently. She may be more nurturing towards her friends, and this could change the group dynamic. For instance, instead of leading the charge all the time, she could be more of a behind - the - scenes organizer, using her new - found femininity to bring the group together in different ways.
One interesting plotline could be Bella's struggle to control her new vampire instincts while still maintaining her relationships with her human friends and family. For example, she might have a hard time being around them without revealing her new nature.