Well, he might gain new powers which could make him more confident. For example, if one of the devil fruits gives him the power of flight, he would feel more powerful and it could change his approach to battles. He might become a bit more adventurous too, as he explores the limits of his new abilities.
He could eat the Pika Pika no Mi (Glint - Glint Fruit) which gives the power of light, allowing him to move at the speed of light and create powerful light - based attacks. And perhaps the Yami Yami no Mi (Darkness - Darkness Fruit) which can absorb other attacks and create a gravitational pull. Combining the powers of light and darkness would be quite a unique and powerful combination for Naruto in this fanfiction.
One potential combination could be if Naruto ate the Ope - Ope Fruit (giving surgical - like powers) and the Inu - Inu Fruit (Dog). He could use the Ope - Ope powers to manipulate his body parts while in his Dog form, perhaps making his attacks more precise or his defenses stronger. This would also open up a whole new set of strategies for him in battles. It's all about how the fanfiction author would choose to blend these very different power sets and how Naruto would learn to use them effectively.
In the Naruto universe, Devil Fruits are from One Piece, and Naruto's world has its own power system like chakra. So, it's highly unlikely in the original Naruto story. However, in fanfiction, anything can happen. The author might create some kind of crossover logic to make it possible, like a strange portal connecting the two universes.
Another fanfiction concept could involve Naruto being sent to the One Piece world through some kind of strange ninja jutsu gone wrong. There, he eats a Logia Devil Fruit that allows him to turn into water. He teams up with the Straw Hat Pirates and uses his water - based powers, along with his ninja knowledge of chakra control, to help them in their adventures. For example, he could use his water form to put out fires on the ship or create water - based defenses against enemies.
The political situation in Naruto's world would be affected too. Countries might start hunting for Devil Fruits to give their ninja an edge. This could lead to wars over the possession of these fruits. In addition, the relationship between humans and tailed beasts might change. Tailed beasts might see those with Devil Fruit powers as a new threat or a potential ally. And ninja villages would need to develop new strategies to deal with the unpredictable nature of Logia - type powers.
If Naruto had the devil trigger in a fanfiction, it would change his character a great deal. His usual carefree and optimistic attitude could be replaced by a more cautious and sometimes even menacing one when the power takes over. He would constantly be at war with himself, between his normal self and the self that the devil trigger brings out. His relationships with his friends might also change. Some might be more wary of him, while others would try to help him through this transformation. And he would have to re - evaluate his ninja way in the face of this new and powerful force inside him.
If Naruto ate a devil fruit, he would gain some amazing new powers. For example, if it was a Logia type like the Mera Mera no Mi, he could turn into fire and use fire - based attacks in addition to his existing ninja skills. This would make him even more formidable in battles.
The powers of devil fruits can be integrated by having characters discover them in a strange new land that has a connection to both the Naruto and One Piece universes. For example, a portal could open up and Naruto and his friends find a devil fruit tree. They then have to figure out how these new powers work within the context of their own ninja abilities. Maybe the devil fruit powers can be combined with chakra to create even more powerful attacks.
His relationship with Sasuke might change. Sasuke is used to Naruto's regular abilities. But if Naruto had devil fruit powers, Sasuke might view him as an even greater rival or, in some cases, a potential threat. He could also be more intrigued by Naruto's new powers and be more likely to team up with him to face stronger enemies.
Naruto's character would develop in many ways. He might become more confident with the new powers from the Logia Devil Fruit. Since these powers are often very strong, he could feel more capable of protecting his village and friends. For example, if he had a lightning - Logia fruit, he could use it to defend against stronger enemies more effectively.