Naruto would adapt to Itachi's life in several ways. Socially, he'd have to get used to Itachi's connections and rivalries. For instance, his relationship with Kisame would be different as Naruto. He might try to influence Kisame in a more positive way. Emotionally, he'd have to deal with Itachi's internal struggles. Itachi had a lot of guilt and secrets, and Naruto would have to either come to terms with them or find a way to resolve them. And in terms of combat, he'd practice Itachi's signature moves over and over to make sure he could use them effectively in battle.
Itachi's personality could become more outwardly friendly. In the ninja world, he had to keep many secrets and be aloof. But in the wizarding world as Harry Potter, he might find it easier to let people in. He may also be more assertive in a different way. Instead of silently following orders like in his past life, he could take the lead in situations, using his own judgment based on his past experiences and newfound magical knowledge.
Yes, there are quite a few. You can start by looking on fanfiction platforms like FanFiction.net or Archive of Our Own. Just search for 'gamer itachi reborn' and you'll find a variety of stories with different takes on the concept.
One common theme is power - up. Since he's reborn as a gamer, he often gains new and enhanced abilities that he uses to his advantage. Another is redemption, as Itachi had a complex past in the original Naruto series, and this new life gives him a chance to make things right in a different way.
A possible plot twist is that Naruto, reborn as Itachi, uses his knowledge of future events to change the Uchiha clan's fate. He could try to expose the real masterminds behind the planned Uchiha coup and prevent the massacre. This would completely change the course of the story, not just for the Uchiha but for the entire ninja world. Also, his relationship with other characters like Kakashi would be very different. Kakashi, who had a certain view of Itachi, would now be dealing with a Naruto - influenced Itachi.
One interesting plot point could be Itachi's unique ninja skills being applied in the wizarding world. For example, his Sharingan might give him an edge in certain magical duels or in detecting hidden magic. Another point could be his interaction with the existing Harry Potter characters. His calm and calculating nature might contrast with the more impulsive Gryffindors, leading to some interesting character dynamics.
One possible plotline could be the OC using her knowledge of the Naruto universe to prevent certain tragedies from happening to Itachi and his family. For example, she might try to stop the Uchiha massacre.
In Itachi yaoi fanfiction, Itachi is often depicted as a complex and mysterious character. He is usually highly intelligent and powerful, which makes him an alluring figure in romantic or relationship - based stories. His loyalty, whether it be to his family, his village, or his love interest in the yaoi context, is also a common characteristic explored.
Well, you can try looking on some popular fanfiction websites like Archive of Our Own (AO3). There might be a good number of fics with this concept there. Just search for the key words and you should be able to find some interesting reads.
The plot could involve the SI using their knowledge from their previous life to protect Itachi. For example, they might try to prevent him from getting involved in the darker aspects of the Uchiha clan's affairs. They could also befriend other important characters in the Naruto universe and use their influence to change the course of events for the better regarding Itachi's life.