There's 'The Elder Naruto'. Here, Naruto's age gives him an edge in understanding the political situation in the ninja world earlier. When dealing with Itachi, who is still involved in his complex web of secrets, Naruto can approach the situation with a more mature perspective. He can start to unravel the truth about Itachi's actions and motives much quicker than in the original storyline.
It changes it significantly. Naruto being older might mean he doesn't idolize Itachi in the same way. He may see Itachi more as an equal or even a rival. For instance, instead of blindly following Itachi's lead in certain situations, he could offer his own solutions based on his more mature judgment.
Typically, these fanfictions often focus on the unique dynamic between an older Naruto and a female Itachi. There's usually a strong emphasis on their relationship development, whether it be a friendship or something more romantic. For example, in many such stories, Naruto's maturity as an older character plays a big role in how he approaches the female Itachi.
There's also 'The Unseen Bond'. In this fanfiction, the female Itachi has a complex personality. The author does a great job of depicting how Naruto, now older, interacts with her. It shows their growth and how they support each other through various difficult situations in the story.
One possible plot development is that Naruto could be involved in the Uchiha clan affairs much earlier. Since he's older, he might have the power and influence to prevent the massacre. He could use his charisma and strength to broker peace between the Uchiha and the village leadership. Another development could be that Itachi becomes Naruto's apprentice of sorts. Naruto could teach Itachi some of his unique jutsu or ways of thinking that are different from the traditional Uchiha teachings.
Well, if Naruto is older than Itachi in the fanfiction, it could lead to a role - reversal of sorts. Naruto might take on a more protective or mentoring role towards Itachi. He could use his experience and power, which he has gained over more years, to guide Itachi in a different way compared to the original storyline.
Another theme is the power of love. It's often shown that their love can overcome the differences between their clans and the past grudges. They support each other in battles and in making important decisions for the ninja world. In some fanfictions, their love is what unites different factions in the shinobi world. A good example is when they use their combined influence to stop a war that was brewing due to old clan rivalries.
One popular 'older Naruto x fem Itachi' fanfiction might be 'Naruto's New Path'. In this story, Naruto has grown older and his relationship with a female Itachi has an interesting dynamic. It often delves into how they work together to face new threats in the ninja world while also exploring their budding romantic feelings.
If Naruto were Itachi's older brother in fanfiction, the power dynamics in the Uchiha clan could be very different. Naruto's influence might prevent the Uchiha massacre. He could use his positive and determined attitude to change Itachi's view of the village. Also, Naruto's relationship with Sasuke would be completely redefined, as he would be Sasuke's older brother's older brother. This could lead to a more united front against the real threats in the Naruto world.
Their family interactions would be quite interesting. Naruto, being the older brother, would probably be very protective of Itachi. He would be the one to stand up for Itachi in family disputes. Itachi, on the other hand, would look up to Naruto and respect his decisions. At the dinner table, Naruto might share his wild adventures in the village with Itachi, and Itachi would listen intently. They would also train together in the family compound, with Naruto pushing Itachi to be better while also making sure he doesn't overdo it.