Yes, in the story Daisy Jones is presented as a real person. The narrative is often crafted to seem like a true account of her life, her music career, and her experiences in the world of rock and roll.
You can try fanfiction.net. It's a large platform that hosts a wide variety of fanfics from different fandoms, and there's a good chance you'll find some Paul Mescal fanfics there. Just use the search function and type in his name.
One popular Paul Mescal fanfic might be those that explore his character in 'Normal People' in different scenarios. For example, some fanfics could be about his character Connell going on further adventures after the events of the show. Another could be a modern - day retelling of his story from a different perspective, like from Marianne's point of view in a more detailed way than in the original work.