In a fanfiction about Naruto, the Gura Gura Fruit, and the Third Shinobi War, perhaps the Gura Gura Fruit is a new, mysterious element introduced into the war. Naruto, being the curious and adventurous ninja he is, might be the first to discover it. His friends and allies could be initially wary of this strange power, but as Naruto learns to control it, they see its potential in turning the tide of the war against powerful enemies such as Orochimaru or the Hidden Stone Village's forces.
One possible plot could be Naruto somehow obtaining the Gura Gura Fruit. He then has to learn to control its powers while still maintaining his own ninja skills. For example, he might accidentally cause earthquakes during battles at first, but as he masters it, he combines the fruit's power with his Rasengan, creating a super - powerful attack.
One possible plot could be that Kushina somehow gains the powers of the Gura Gura no Mi. She could use it to protect Naruto from various threats in the Naruto universe. Maybe she could create powerful shockwaves to fend off enemies like the Akatsuki. Naruto, seeing his mother's new power, would be inspired to train harder and learn how to combine his own jutsu with the power of the Gura Gura no Mi.
Naruto could use the Gura Gura Fruit to create huge tidal waves in battles near water sources. This would be a great advantage against enemies not used to fighting in water. For example, if facing the Sand Village ninjas, he could flood the desert battlefield, disrupting their attacks and movements.
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.
Their relationship could become stronger. Kushina, with the Gura Gura no Mi, would be an even more powerful protector. Naruto would look up to her even more, and they would bond over the new power she has. He might ask her for training tips on how to use such a powerful ability.
Well, Vegeta would be a likely character. He might be initially suspicious of the female Goku. Maybe he thinks she's a threat or just can't believe there's another Goku - like being. He could be there to add some comical moments as he tries to understand the situation.
In general, it's a bit of a toss-up. The strength of Manga Goku and Anime Goku can vary depending on the specific arcs and battles. Sometimes, it might seem like one is stronger in a particular situation, but that could change in another.