There are many out there. A really good one might focus on the emotional reactions of Team Minato. For example, Minato might be proud of Naruto's strength and how he overcomes Pain. Kakashi could be in awe at Naruto's new techniques. Their reactions can enhance the overall viewing experience in the fanfiction.
You can try looking on popular fanfiction websites like FanFiction.net or Archive of Our Own (AO3). They usually have a wide range of Naruto - related fanfictions, and you should be able to find some with the 'Team Minato Watches Naruto vs Pain' concept.
He could feel it through a shared chakra link. Since they are related and Minato sealed the Nine - Tails in Naruto, there might be a latent connection that gets activated in the fanfiction, allowing him to sense Naruto's pain on a physical and emotional level.
The 'jiraiya vs pain' in RWBY fanfiction could be a battle of wits as much as a battle of powers. Jiraiya is a very experienced ninja, and Pain has his own ideology - driven powers. In a RWBY setting, the battle could be affected by things like Dust, the special energy source in RWBY. Jiraiya might be confused by this new element at first, while Pain could try to incorporate it into his attacks. It would be a clash of two different power systems and fighting styles.
The plot could involve Minato being brought back to life or having a vision where he steps into Naruto's shoes. He might feel Naruto's pain from constantly being underestimated because of his status as a Jinchuriki. This could lead to Minato trying to find ways to comfort Naruto from afar, or even influencing the events around Naruto in a supernatural way.
The biggest difference is the creativity of the fanfiction writers. In the anime, the fight follows a set storyline. But in fanfiction, anything can happen. For example, Naruto could suddenly gain a new power that was never in the anime. It's like a whole new world of possibilities.
Konan could be really interesting. In some fanfictions, she might have a different backstory or motivation that affects the Naruto vs Pain fight. For example, she could be secretly trying to stop Pain from going too far in his destruction of the Leaf Village.
It's really hard to say. Minato is extremely fast with his Flying Raijin and is a very intelligent fighter. But Naruto has an incredible amount of chakra, his Sage Mode, and his Six Paths powers. If Naruto can get close enough to Minato, his brute strength could overpower Minato. However, Minato's speed and strategic mind might keep Naruto at bay.
In some 'minato vs naruto fanfiction', there could be a scenario where they battle in a different dimension. Minato uses his Flying Raijin to quickly move around and Naruto counters with his shadow clones and massive Rasengan attacks. Also, a scenario where they fight not as enemies but in a friendly spar to teach Naruto some secret family jutsu that only Minato knew would be really cool.
It's really hard to say who would win. Jiraiya has his Sage Mode which gives him enhanced strength, speed, and perception. But Pain has the Rinnegan which allows him to use powerful abilities like the Six Paths techniques. In the RWBY fanfiction context, it might depend on how well they adapt to the RWBY world. If Jiraiya can quickly figure out how to use Dust to his advantage, he might have an edge. But if Pain can use his powers to disrupt the balance of the RWBY world, he could also come out on top.