In the comics, Barry Allen and Iris have a complex relationship. Sometimes they face challenges and separations, but ultimately, they often find their way back to each other.
Iris remains alive in the Flash comics. The creators have kept her as an important and ongoing presence, and her role continues to evolve and contribute to the overall narrative.
One common theme is the exploration of their shared history. In many fanfictions, the authors go back to their childhood memories and how those experiences shaped their relationship. Also, the theme of trust is quite prevalent. Since they are in a relationship that has its own set of challenges, showing how they build and maintain trust is a big part of these stories. There's also the theme of hope, that no matter what difficulties they face, they always have hope for their future together.