I'm not entirely sure about the exact plot of the 'william afton fnaf graphic novel' as I haven't read it yet. But generally, in the Five Nights at Freddy's universe, William Afton is a key and rather sinister character. So, it might revolve around his actions, his backstory, and how he relates to the spooky events in the Freddy Fazbear's Pizza places.
Besides William Afton, the 'william afton fnaf graphic novel' could feature a host of characters. The animatronics are likely to be major players. Freddy, with his leadership among the animatronics, might be important. Bonnie, the guitar - playing bunny, and Chica, the chicken. There could also be human characters such as the original founders of the Freddy Fazbear's franchise who might have had some connection with Afton. Additionally, any characters who have tried to solve the mysteries surrounding the spooky events at the pizza places could be part of the main cast.
In the Legend of William Tell, William Tell was a brave Swiss man. He was known for his amazing crossbow skills. He was put in a difficult situation by the Austrian authorities where he had to prove his skill by shooting an apple off his son's head. His actions later led to a revolt against the Austrians.
Definitely not a true story. FNAF is a work of fiction that takes place in a fictional world with its own set of rules and scenarios. It's all about creating a thrilling and immersive gaming and storytelling experience, not reflecting reality.