If Sasuke had the Fire - Fire Fruit, his fire - based attacks would become much more powerful. His Amaterasu could potentially be even more destructive, as the Fire - Fire Fruit's flames might add an extra level of intensity. His fighting style would become more aggressive, relying on the overwhelming power of the fruit's fire to overpower his opponents.
If Naruto had the Fire Devil Fruit, his combat style would change drastically. He could combine his existing ninja skills with the power of the fruit. For example, he might be able to infuse his Rasengan with fire, making it even more powerful. Also, his mobility could be enhanced as he could use fire to propel himself in new ways. This would make him a more formidable opponent in battles against strong foes like Sasuke or Pain.
The Fire Devil Fruit could make Naruto more confident. Having such a powerful ability would give him an edge in battles and make him feel more capable. This newfound confidence could also change how he interacts with his friends and allies. He might be more assertive in leading them.
His fighting style would become more diverse. If he got a devil fruit, say the Ope Ope no Mi (Operation - Operation Fruit), he could create rooms and manipulate objects within those rooms. This would be a huge departure from his normal ninja attacks. He could trap enemies in these rooms and then use his kunai and shuriken skills within the confined space to defeat them.
His fighting style would become more diverse. If it was a Paramecia devil fruit, say the Gomu Gomu no Mi, he could stretch his limbs like Luffy. This would add a whole new dimension to his close - combat skills, allowing him to reach enemies from a distance and perform acrobatic attacks that his normal ninja training might not have included.
Naruto's fighting style would change significantly. The Master Sword is a melee weapon, and Naruto is not used to relying on such a weapon. He would have to learn new footwork and combat stances. He could start using the sword as an extension of his arm in close - quarters combat. Also, he could use his shadow clones to create diversionary attacks while he strikes with the sword from unexpected angles.
If Naruto had fire fist powers in fanfiction, his combat style would be completely different. He could use the fire fists for both close - range attacks and long - range by shooting out fire projectiles. This would make him a more versatile fighter.
Naruto would become more powerful, and this might make him a bit more cautious. He's used to his regular ninja abilities, but the gura gura fruit's power is on a different level. He might be more hesitant in battles at first, not wanting to accidentally cause too much destruction with the fruit's earthquake - causing ability.
He would likely be more isolated at first. The Magu Magu Fruit powers are different from normal ninjutsu. His friends might not understand it fully, and he would need time to master it alone. This would make him more introspective, but as he gets better control, he would start to share his knowledge and use it for the good of the village. Also, his fighting style would change drastically. Instead of relying solely on his shadow clones and Rasengan, he would incorporate the heat - based attacks of the Magu Magu Fruit, making him a more versatile fighter.
His fighting style would likely incorporate more acrobatic moves. Since the Keyblade can be used for things like jumps and dashes in mid - air, Naruto would start using these abilities. He might also use the Keyblade to block attacks more effectively than he could with just his kunai or shuriken. And he could use the Keyblade's power to enhance his speed, allowing him to quickly close the distance between him and his opponents or dodge attacks more easily.
His fighting style would become more versatile. Naruto is used to his shadow clones and Rasengan techniques. But with Samehada, he could add a whole new dimension. Samehada absorbs chakra, so Naruto could use it to drain his opponents' chakra during close combat. He might also be able to combine his own chakra with Samehada's absorption ability to create some unique attacks that are more about disabling the enemy's chakra system rather than just physical damage.