Well, in many fanfictions, Naruto might use his strong will and the power of his Uzumaki heritage. His natural chakra reserves are huge, which helps. He also has a deep understanding of friendship and the tailed beasts' pain from his own experiences. So, he can connect with them on an emotional level and gradually gain their trust, thus being able to control them.
Naruto is obviously one of the most popular characters. Since he has a strong connection to the tailed beasts in the original series, in fanfiction, he often takes on even more heroic and complex roles related to them.
Another plotline might involve the tailed beasts teaming up in a way that was unexpected. Say, all the tailed beasts decide to break free from their jinchuriki hosts at the same time and form their own alliance. This would create a huge shift in the power balance in the Naruto universe and force the ninja villages to reevaluate their relationships with the tailed beasts.
One great fem Naruto x fem Kyuubi fanfiction could be one that focuses on their unique bond. It might explore how they interact in a world where Naruto is female and the Kyuubi also takes a female form. For example, it could show them teaming up against common enemies and how their combined powers are different from the original story.
One possible plot could be that the female werewolf is an outcast in her own world. Naruto, with his kind heart, befriends her. Meanwhile, the fem Kyuubi has a connection to Naruto due to the Kyuubi within him. They all come together when a common enemy threatens the Hidden Leaf. The werewolf could use her unique abilities, like enhanced strength and speed, to help Naruto in battles, while the fem Kyuubi might offer her own brand of power, perhaps related to chakra manipulation. As they fight side by side, a deep bond forms between Naruto and the two female characters.
A prevalent theme is also acceptance. Naruto has to accept these two unique entities into his life, and they in turn have to accept him and each other. It's about how different beings from different backgrounds can come together. And there's often the theme of adventure as they go on various quests or face threats in the Naruto world.
The plot should be engaging. It could involve a new threat to the ninja world that only fem Naruto and fem Kyuubi can stop together. This could lead to a lot of action - packed scenes and also some really touching moments between them as they rely on each other. A good fanfiction might also explore their backstories in this new context, like how fem Naruto came to terms with having the Kyuubi inside her as a female.
In such fanfiction, Naruto may gain the ability to heal himself more quickly. Since the tailed beasts possess a great amount of life - force energy, Naruto could tap into that to accelerate his own healing process. His mental abilities could also be enhanced. He would be able to withstand greater mental pressure and use the tailed beasts' collective wisdom to make better decisions in battles. Moreover, he could potentially create a chakra shield that is extremely strong, using the combined chakra of all the tailed beasts to protect himself and his allies.
I'm not sure specifically as there could be many different takes on it. It might be about a character who has a special connection or power related to the tailed beasts, like being able to control them in unique ways or having some sort of prophetic knowledge about them.
The relationship between Naruto and the fem werewolf could start as a friendship based on mutual respect for each other's abilities. Naruto would be intrigued by her werewolf powers. With the fem Kyuubi, Naruto already has a complex relationship due to the Kyuubi inside him. As the story progresses, the fem werewolf might develop romantic feelings for Naruto, which could make the fem Kyuubi a bit envious at first. But eventually, they could all form a strong, platonic bond where they support each other in different ways, like in battles or in dealing with the politics of the Hidden Leaf.