In his relationships with the magical community outside of Hogwarts, his cleverness would make him a more prominent figure. Wizards and witches would look up to him as a young prodigy. This could also attract the attention of some dark wizards who might see his intelligence as a threat. But it also means that he has more resources at his disposal. He could use his intelligence to make connections with influential wizards and use their influence to further his own goals, like improving the conditions of house - elves or reforming the Ministry of Magic.
His intelligence might make him more respected by his peers. Instead of just being known for his scar and his connection to Voldemort, his friends see him as a true intellectual. Hermione might become more of an equal to him in terms of academic discussions rather than just being the one who always has the answers. Ron, on the other hand, could feel a bit intimidated at first but then grow to be proud of his friend's intelligence.
With his teachers, his cleverness could lead to more special attention. Dumbledore might take him under his wing even more, sharing deeper secrets of magic and the wizarding world with him. This could also cause some jealousy among other students, especially those from Slytherin who might see Harry as a threat not just in terms of his power but also his intelligence. However, Harry could use his intelligence to bridge the gap between the houses, for example, by starting study groups that include students from all houses.
With his friends, it could initially cause confusion. They are so used to calling him Harry that the new name might be a bit of a shock. But if they understand his reasons, they would likely support him. For example, Hermione might be the first to adapt and help others adjust, using her logical thinking to see the benefits of the name change.
It might make his friends a bit wary at first. Since this is an unusual and powerful thing to happen, they could be concerned about how it's changing Harry. But as they see that Harry is still the same person deep down, they would gradually accept it.
His intelligence might make his relationships more complex. With his friends, they could look up to him for his smarts. For example, they might come to him for help with their studies or for solving problems. But it could also create a bit of distance at times. If he's always thinking several steps ahead, his friends might have a hard time keeping up with his ideas.
If Harry absorbs the memories of his enemies, it could make his relationships with other characters more complicated. For instance, if he absorbs the memories of Draco Malfoy, he might understand Draco's family pressures better. This could lead to a more complex relationship where Harry has both sympathy and still some animosity towards Draco.
His relationship with Ginny might be affected. Ginny could be very protective of him and worry a great deal. This could lead to some sweet, tender moments between them as she takes care of him during his seizures.
In this fanfiction scenario, Harry's relationship with Dumbledore could be very interesting. Dumbledore would surely be aware of the significance of Excalibur. He might take Harry under his wing even more, guiding him on how to use the sword's power for good. Harry's relationship with the other Hogwarts students could also change. Some might look up to him even more, while others might fear him because of the great power he now wields.
If Harry is sleepwalking, it might worry his friends. For example, Hermione would probably be very concerned and try to find a way to stop it. This could strengthen their friendship as she devotes time to helping him. Ron, on the other hand, might initially find it funny but then also realize the seriousness. It could also make some of his classmates more curious about him, which could either bring them closer or create some distance depending on how they react to his sleepwalking episodes.
If Harry changes his look to seem more intimidating, it might make some of his enemies more cautious around him. For example, if he has a more severe look with a long beard and a scowl, the Death Eaters might think twice before attacking him. As for his friends, they might be a bit taken aback at first but would quickly accept the new look.
His friends might be initially terrified. Hermione, for example, would be both scared and immediately start researching how to reverse it. Ron would probably be more shocked and not know how to react at first. Their friendship would be tested as they try to figure out what to do. They might have to keep Harry's transformation a secret from other students to protect him from being hunted or experimented on.
His relationships with his teachers could also change. Dumbledore might look at Harry with more sympathy and offer him different kinds of guidance. Snape, although still prickly, might secretly respect Harry more for enduring this new hardship, or he could use it as an excuse to be even more critical, thinking that Harry is now more likely to make mistakes.