Well, it could be about an original character (oc) who dies in their own world and is reborn in the Bleach universe. Maybe they have some special powers from their previous life that make them stand out in the new world of Hollows, Soul Reapers and Quincy. They might start off as a normal human in Karakura Town and then gradually discover their connection to the spiritual world.
It could be a powerful Arrancar. In the Bleach universe, Arrancars are often antagonists. A particularly strong and cunning one might see the oc as a threat to their plans. Maybe the oc's presence disrupts the Arrancar's scheme to take over a certain part of the Soul Society or gain more power.
The plot could involve Naruto and Hinata being reborn as Shinigami. Naruto might be a hot - headed but talented Shinigami, quickly rising through the ranks. Hinata could be in a different division, perhaps the 4th division due to her healing - like nature. Their relationship could develop further as they face challenges in the Soul Society. They could also encounter some Bleach villains who mistake their chakra - based powers for some new and dangerous spiritual abilities, leading to some intense battles.
Naruto's ability to use the Nine - Tails' chakra could turn into something like having a powerful spiritual beast companion in the Bleach world. Hinata's Byakugan could be enhanced to see spiritual auras more clearly and detect hidden spiritual threats. Their powers would also be influenced by the fact that they are now in a world with Shinigami, Hollows, and Quincy. They might learn new techniques from the Bleach characters and combine them with their own unique abilities.
In my opinion, both have their merits. The anime brings the characters to life with animation and sound, but the manga allows for more imagination and detail in the panels. It really comes down to what you value more in your entertainment.
Bleach is not a novel. It's more famous for its manga and anime versions. The manga format allows for a more visually dynamic and action-packed presentation of the story compared to a traditional novel.
Rukia would probably be very critical at first. Since she is quite serious, she might nitpick the inaccuracies in the fanfiction. But she might also secretly enjoy the ones that show her in a positive light, like those highlighting her friendship with Ichigo. In the Bleach universe, characters are used to their own stories, and fanfiction would be a whole new and unexpected take on their lives. The zanpakuto spirits might also have interesting reactions if they could read, as they have their own personalities and might be offended or flattered by how they are depicted in the fanfictions.