Goku's personality as Naruto would be an interesting blend. His simple - mindedness in terms of food and training would remain, but now it would be expressed through Naruto's love for ramen and his intense training sessions. His sense of loyalty, which was strong in Dragon Ball towards his friends, would be amplified as Naruto, who has a deep connection to his village and comrades. Also, Goku's lack of concern for formalities might clash a bit with Naruto's need to conform to some ninja traditions at times, creating humorous and character - developing situations.
When Goku is reborn as Naruto, his personality could shift in several ways. His naivete might be toned down a bit as he has to adapt to the more nuanced world of Naruto. He may become more empathetic towards the villagers' plights since Naruto has his own backstory of being an outcast. However, his love for challenges and growth in power would still be there, but now it would be more intertwined with Naruto's goals of protecting the village and achieving peace in the ninja world.
Naruto might become more calm and collected. Goku has a certain simplicity and focus in his personality. Naruto could pick up on that and not be as impulsive as he usually is.
Naruto's personality might show a more serious side. Wearing a suit could make him feel more responsible, like he has to represent the Hidden Leaf in a proper way. So he'd be less likely to crack jokes and more focused on the task at hand.
Naruto might become more calculating. Since Mewtwo is very intelligent and has powerful psychic abilities, Naruto would have to use his mind more. He would think before acting, unlike his impulsive self in the original series. This change could make him a better strategist in battles, but it could also lead to misunderstandings with his friends who are used to his more straightforward and impulsive nature.
Naruto's personality could shift towards being more reserved. As a Shinigami, he has to deal with the weight of handling souls and the concept of death. This could make him think twice before acting impulsively like he used to. He may also develop a more empathetic side towards those who are about to die or have lost loved ones, as he now has a closer connection to the afterlife.
His personality would change in several ways. For one, he'd have to be more cautious. Obito was involved in a lot of secretive and dangerous operations. Naruto would have to adapt to this new level of secrecy. Also, he might become more brooding as he tries to understand Obito's darker motives in the original story. But ultimately, his strong belief in friendship and his never - give - up attitude would still be there, and he'd use them to make different choices than Obito did.
His personality would be a blend. He would have Kakashi's calmness in high - pressure situations. But at the same time, Naruto's exuberance would peek through at times. For instance, when he's around his friends or when he's really passionate about something. He would be more introverted in general but would still show his Naruto - like enthusiasm on certain occasions.
Naruto's love for his friends and his village would translate into a new form in this rebirth. He might see the people in the Dragon Ball universe as his new family and friends. His outgoing and friendly nature could start to break down the walls of fear that Frieza had created. He would be less likely to immediately resort to violence like the old Frieza, instead trying to talk things out first, but still be ready to fight if necessary to protect those he cares about.
His temper might be more volatile. The Kyuubi's influence could make him quicker to anger, especially when someone threatens his friends or the village. However, he also has better control over his emotions in other cases as he has to manage the power of the Kyuubi. He can't let his emotions run wild all the time. He might be more withdrawn in some aspects, spending time to understand and control the new power within him, rather than being as outgoing as he was before.
If Naruto becomes a Hunter Nin in fanfiction, his personality would change significantly. He'd be more calculating. His usual impulsive nature would have to be toned down because one wrong move as a Hunter Nin could mean disaster. He might also become more solitary, used to working alone in the shadows rather than in a team. His sense of humor might also be more subdued as he takes on this serious and dangerous role.
Naruto might become a bit more reserved at first. Since Tsuna's world is different from Naruto's, he'd have to adapt. But his core of being kind - hearted and determined would remain. He might be more cautious as Tsuna initially isn't as bold as Naruto was in his own world.