One unique aspect is the exploration of his dual nature. In fanfictions, we can see how his human side battles with his werewolf instincts. For example, in some stories, he has to fight the urge to harm his friends during a full moon. Another aspect is the way his lycanthropy affects his relationships. Some fanfics show how his condition makes him feel isolated from others, like he doesn't truly belong in the wizarding community.
The unique aspect in many fanfictions about Remus as a werewolf is the exploration of his place in the wizarding society's hierarchy. Since werewolves are often discriminated against, these stories show how he tries to rise above that. Some fanfictions also look at the magical remedies and potions related to his condition in new ways. They might create new spells or potions that could help him control his transformations better. Moreover, the relationships he forms with other werewolves in fanfictions can be really interesting. It gives a different view of the werewolf community within the Harry Potter world that we don't get much of in the original books.