Sure, Kakashi is present in the Boruto manga. His role might not be as prominent as in the Naruto series, but he still has significant moments and interactions.
Kakashi is very much alive in the Boruto manga. The manga doesn't include his death. Maybe you got some misinformation or confused it with another character's fate. But for sure, Kakashi is around.
If Naruto was the same age as Kakashi, the power dynamics would be very different. Naruto might be more skilled and mature from the start. He could have been part of the earlier battles against the Akatsuki. Also, his relationship with Sasuke might have a different flavor as they would be closer in age and experience. For example, they might be more like equals in their rivalry, rather than Naruto constantly chasing Sasuke's level of skill.
If Naruto was the same age as Kakashi, his character development would take a different path. He would have likely faced different traumas and challenges growing up. For example, he might have been more directly involved in the Third Hokage's reign and the events that led to his death. This would have made him more politically aware and perhaps more cynical. Also, his relationships with his peers would be different. He might not have had the same close - knit group of friends as he does in the original story, as his age difference would put him in a different social circle.
One possible plot could be that Naruto is already a respected ninja in the village. He's assigned to a special mission to deal with a new threat that's related to an old enemy of Kakashi's. Since he's at Kakashi's age, he has the skills and knowledge to handle complex situations. Along the way, he discovers secrets about his own past that are linked to this new threat. He has to use his experience and the bonds he's made over the years to overcome the challenges.
The plot of such a fanfiction could also explore how the ninja world views them. Since Sakura is now in Kakashi's position age - wise, she could be given more dangerous and important missions. She would have to deal with the political aspects of the ninja world. Meanwhile, Kakashi as a young ninja might be underestimated at first, but then prove his worth in unexpected ways. Their age - swap could also lead to different power developments, as their bodies and minds are now in different states compared to their original ages.
If the protagonist of Naruto was the same age as Kakashi, they might have met when they were young and attended the ninja school training together. As time passed, they might grow up together and meet under some opportunity to start a thrilling story.
In a more light - hearted plot, Fem Naruto and Kakashi could start a friendly prank war in the village. Since they are the same age, they might have a similar sense of humor. This could lead to some hilarious situations where they constantly try to out - prank each other, but also learn important lessons about friendship and respect in the process.