Well, Harry would likely be much more confident at Hogwarts. With his parents alive, he would grow up in a loving and magical home environment. This would translate into his school life. He would probably be more social and make friends more easily. He might also be less likely to get into dangerous situations with Voldemort. His parents could even be involved in the school in some way, like teaching a special class or being on the board of governors. This would give Harry a certain amount of privilege and protection that he didn't have in the original story.
Harry would grow up with his parents, which means he would have a much more stable and loving childhood. He would not have to face the Dursleys' abuse. His parents could teach him magic from a very young age, so he might be more advanced in his magical abilities. Also, he would have a strong family support system, which could make him more confident and less self - doubting.
Harry would likely enter Hogwarts with a more confident and carefree attitude. His parents could have given him valuable advice about the school, like which professors to befriend and which ones to be cautious of. He might also have some family - related advantages, such as access to special magical items passed down from the Potter family. And without the shadow of his parents' death, he could fully enjoy his time at Hogwarts, participate in more school activities, and not be as isolated as he was in the original story.
Harry would likely be more confident. With his parents alive, he would grow up with their love and support, not having to face the same insecurities. He might be less impulsive as he would have their guidance. For example, he wouldn't have to jump into dangerous situations alone as he'd have his parents to back him up.
Well, he'd probably be more of a legacy student. He might be treated with even more respect or envy from the start. And he could have a different group of friends. Instead of Ron and Hermione, he might be closer to his brother's old gang, like Sirius and Remus, from the very beginning at Hogwarts.
Well, it could make Harry feel a strange connection to the spirit world at Hogwarts. He might be more attuned to the ghosts there, seeking advice from them as if they were his parents. It could also make him a bit of an outcast as his situation is so unusual. Maybe he'd have special powers related to interacting with the spirit realm that others don't have.
In a fanfiction where Lily and James Potter are alive, the plot would be turned on its head. For starters, the Dursleys would never have come into the picture. Harry would have been raised in a loving magical family. This would mean he'd have access to all his magical knowledge and abilities from a young age without any suppression. Also, the war against Voldemort would have been fought very differently. Lily and James, being experienced and powerful wizards, would have led the charge. Their presence would have inspired a different kind of hope in the wizarding community. And think about Hogwarts - Harry would be going to school with his parents' support and influence, which could change how he interacts with his classmates and teachers.
He'd be more confident. With a loving mother around, he wouldn't have the insecurities that came from growing up with the Dursleys.
Their spirits often interact in subtle ways. For example, when Harry is exploring the Forbidden Forest, he might feel a warm breeze when there shouldn't be one, which is actually James looking out for him. Lily, on the other hand, could influence his dreams, giving him advice or just showing him loving memories when he's feeling down.
His diet at Hogwarts would be a major change. Instead of eating normal food, he would need blood. He might have to find some discreet way to get it. His sleeping habits could also be different. And he would probably be the center of a lot of rumors and fear among the students.
His classes would be a struggle. For example, in Potions, the smell of the ingredients might be overwhelming to his new vampire senses. And in Defense Against the Dark Arts, he might have a new perspective on dark creatures since he is now one of them.