There are fanfics that center around the mystery - solving aspects within the wizarding world. They might involve Harry and his companions trying to figure out ancient spells or the secrets of certain magical artifacts. These are much more positive and appropriate compared to inappropriate ones.
I'm not sure if there are specific 'harry stuffs hermione fanfic' available. You can try searching on some popular fanfiction websites like FanFiction.net or Archive of Our Own. They have a vast collection of Harry Potter fanfictions, but it might take some time to find the exact ones you're looking for.
There are also fanfics that explore the backstories of other minor characters in the Naruto universe, like how they got into the ninja academy and their dreams before becoming full - fledged ninjas. This kind of fanfic gives more depth to the overall Naruto world.
I have no idea if it's popular. There are so many fanfics out there, and just from this title alone, it's difficult to gauge its popularity. It might be a niche fanfic that only a small group of people who are really into the specific fandom or the unique concept it presents are interested in.
There's no way to know for sure who Harry is just from this title. He could be an original character created for the fanfic, or he could be a character borrowed from another work and being used in a new way within this fan - created story.
I haven't actually read a 'harry stuffs hermione fanfic' myself. But generally, fanfics can range from being really well - written with great character development to some that are just for fun and not as polished. In this case, it would likely be a story that focuses on interactions between Harry and Hermione in a way that might not be in the original books.