Another plot could be a love triangle situation. Maybe Allison was previously involved with someone else, and her growing feelings for Isaac create a lot of tension. The kiss between them then becomes a turning point in the story, either making things more complicated or starting to resolve the love triangle in some way. In some fanfictions, this kiss could be a secret at first, adding an element of mystery and drama to the plot.
You can try searching on popular fanfiction websites like Archive of Our Own (AO3) or Fanfiction.net. These platforms usually have a wide range of fanfictions, and by using the relevant tags such as 'Isaac', 'Allison' and 'kiss', you might be able to find the fanfictions you're interested in.
In some fanfictions, their kiss might be a turning point. For example, it could lead to them facing challenges together as a couple. They might have to deal with family reactions, like how Max's family of superheroes would react to him dating Allison. And also, it could be a catalyst for their own personal growth, pushing them to be better versions of themselves.
Expect there to be some sort of conflict. Maybe there are other characters who don't approve of their relationship. Or perhaps there are secrets between them that surface after the kiss. This conflict would add drama and keep the readers hooked. For example, if Allison discovers that Max has some hidden superhero responsibilities that could put her in danger.
You can start by looking on fanfiction.net. It has a large collection of Teen Wolf - related fanfictions, and there are likely many that include Stiles and Allison's kiss.
One great fanfiction could be 'Unexpected Moments' where their kiss is a turning point in a dangerous situation they're in. It really builds on the tension between them.
A common theme is their relationship development. Since they have a complex relationship in the original story, fanfiction often delves deeper into how they overcome their differences and grow closer. Another theme is the exploration of their powers in relation to each other. For example, how Jackson's werewolf abilities and Allison's archery skills could be used together in different scenarios.
Love and loss are common themes. Since Allison's death in the series, many fanfictions explore how Scott copes with losing her, and also how their love endures. Another theme is the struggle against the supernatural world. They often face threats together, and this is a big part of their relationship in the fanfictions as well.
The theme of self - discovery also pops up. Allison might discover new sides of herself in the Naruto world, and Naruto may also learn something new about himself through his relationship with Allison. This could be related to their abilities, values or how they view the world around them.