Well, Kakashi's abilities would change in interesting ways. Since he has experienced many battles in the future, his reflexes would be sharper. His ability to strategize would be far superior. He could use his future knowledge of his opponents' techniques to his advantage. For example, if he knew a particular enemy's weakness from the future, he could use that knowledge to defeat them more easily in the past. Also, his chakra control, which was already good, could be even more precise, allowing him to perform more complex jutsu.
Kakashi's abilities would likely be enhanced in the past. He has all the knowledge and skills he's gained in the future. So, his combat skills would be more refined. His Sharingan would be even more powerful as he would know better how to use it. He might also be able to teach his younger self some new jutsu that he learned over the years.
Their relationships would likely become stronger. They would have to rely on each other more in the unfamiliar past environment. For example, Naruto might look up to Kakashi even more as he sees how much Kakashi has grown and changed. Sasuke might be more open to the idea of teamwork as they face challenges together in the past.
Obviously, Kakashi is one of the main characters since it's about his time travel. Minato is also a central figure as he is part of Team Minato that Kakashi travels back to be with. And of course, the other members of Team Minato like Obito and Rin are likely to be important characters as well.
Minato would probably be very proud. He always saw potential in Kakashi, and seeing his future accomplishments in the fanfiction would confirm his belief in him. He might have a big smile on his face and feel a sense of accomplishment as if he had a part in shaping Kakashi into who he becomes in the future.
A really cool plot might be that Kakashi time travels and discovers a hidden conspiracy in the past that was related to Team Minato. He then has to work with his past comrades, including Minato, to uncover the truth and prevent a great disaster that he knew about from his own time.
One good plot could be Kakashi going back in time and using his future knowledge to prevent the death of his comrades in Team Minato. For example, he might be able to stop Obito from getting crushed in that rockslide. Another plot could involve him trying to change the course of the war by influencing key decisions made by his team. He could also go back and try to train himself better in the past, using the skills he's learned in the future.
Kakashi from the future would be a bit reserved at first. He has seen a lot and might not want to reveal too much too soon. But as the conversation progresses, he would start opening up. He could share stories of their future battles and how each member of Team Minato played a crucial role in the future of the village. For example, he might tell Obito how his self - sacrifice was not in vain and had a great impact on the village's future. This would strengthen their bond as a team and give them a new sense of purpose.
They would probably be shocked at first. After all, seeing a future version of someone they know is quite unexpected.
Emotionally, it would be a powerful encounter. They might share their feelings about the losses they've all faced, like the death of Minato. This could strengthen their relationships and also give Kakashi new insights as Hokage on how to protect the village better.
In the past, Team RWBY's abilities could change in various ways. Ruby's semblance of speed would give her an edge in battles, but she might also attract unwanted attention as people in the past may not be used to such swift movements. Weiss's Glyphs could potentially be more powerful in the past if the Dust in that era has different properties. Blake's ability to create clones could be misinterpreted as some kind of dark magic, causing her to have to be more careful about using it. Yang's power might be more difficult to control as the technology to understand and manage it might not exist, making her a bit of a loose cannon in the past.
Probably Naruto. Since Minato is his father, he has always longed to know more about him. Meeting Minato and his team would be a dream come true for Naruto. He would be eager to hear stories from his father's past, about his training, and how he became such a great ninja. Naruto might also want to show off his own skills to his father and the rest of Team Minato.