Common themes include the struggle for acceptance, not just from society but also from his own friends and family. There's also the exploration of his bisexuality in some fanfics (as some interpretations see Peter as bisexual). His relationships are often explored in depth, from the initial attraction to the challenges of maintaining a relationship while being a superhero. These fanfics also often deal with themes of discrimination and how Peter overcomes it.
Well, a big theme is identity crisis. In many of these fanfics, Peter struggles with how his gay identity fits in with his image as Spider - Man. Also, the theme of secrecy is common. Just like he has to keep his superhero identity a secret, he may also have to hide his sexual orientation, at least at first. There's also the theme of finding a community, of other LGBTQ+ characters who support him.
One common theme is self - acceptance. Peter often has to come to terms with his sexual orientation while also dealing with his superhero identity. Another theme is love and relationships, exploring how he forms romantic connections in a world that may not always be accepting.