In terms of his classes, Defense Against the Dark Arts would be a whole new experience. He could use his Saiyan powers to counter dark magic in ways that no one has ever seen before. He might even develop his own unique spells that are a blend of magic and Saiyan energy, making him a truly formidable wizard - Saiyan hybrid at Hogwarts.
He'd probably have a hard time fitting in his dormitory. I mean, he might be too big for the bed! Also, Quidditch would be a whole new ball game. He could accidentally destroy the brooms or the goalposts with his strength. And the other students would likely be either in awe or terrified of him.
In this fanfiction, Harry's life at Hogwarts would be full of new discoveries. He could find secret passages that are overgrown with plants but are only visible to him because of his connection to Demeter. His friends might be a bit in awe of his new powers. He'd also have to deal with some jealousy from other students who don't have such unique abilities. And when it comes to Quidditch, he could use his nature powers to his advantage, like creating a gentle breeze to help him fly faster or making the grass on the pitch grow in a way that confounds his opponents.
He would become more confident. Saiyans are known for their pride and confidence in their power. Harry, with Saiyan blood, would likely carry himself differently. He'd be more willing to take on challenges head - on without as much hesitation.
His physical abilities would be enhanced. He'd be much stronger and faster than normal wizards. So, in Quidditch, he'd be an even more formidable Seeker. Also, his Saiyan anger could be a double - edged sword. It might help him in a fight but could also cause problems if he loses control.
Well, it would change a great deal. For one, he might get better grades in Potions as Snape would be more likely to give him extra help. Also, he might be more protected from the likes of Draco Malfoy and his gang, since Snape would not tolerate any bullying towards his adopted son. Harry could also have access to Snape's private library, which would expand his knowledge of magic far beyond what he could learn in the regular Hogwarts curriculum.
Godric Gryffindor's view might not change much. He'd still see Hogwarts as a place to foster courage, but he might gain new insights from the fanfiction about how students in modern - day interpretations uphold that value. Salazar Slytherin could become more cynical. If he saw his house being misrepresented in some fanfictions as all - evil, he might think Hogwarts has strayed from his original intentions. Helga Hufflepuff would probably feel more positive. The fanfiction that emphasizes kindness and hard work would make her believe Hogwarts is still a great place for nurturing good values. Rowena Ravenclaw might be more open - minded. She'd see different perspectives on Hogwarts in the fanfiction and might consider new ways of teaching and learning in her view of the school.
The story would be drastically different. Without Harry, there's no Boy - Who - Lived to be the main antagonist to Voldemort. Hogwarts might not be the safe haven it was in the original series. Voldemort could target the school more directly, and the students would live in constant fear.
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.
He'd likely have to keep his vampire identity a secret. He might not be able to participate in some daytime activities or classes that take place outdoors during the day. His diet would be a huge issue, having to find a way to get blood without being discovered.