Harrison Bergeron is the protagonist in the story. He is a young man who has extraordinary abilities, both in terms of physical strength and intelligence. He rebels against the society's forced equality by breaking free of his handicaps.
Harrison Wells isn't part of the comic world. He's unique to the TV adaptation. The show introduced him as a new element to the story, separate from the comic source material.
One common theme is family loyalty. Since they are siblings, a lot of fanfics explore how they would do anything to protect each other. For example, in many stories, Oliver will go to great lengths to keep Thea safe from the threats in their city.
I'm not sure which specific 'Barry and Thea love fanfiction' is the best, but you can try looking on fanfiction websites like Archive of Our Own. There are often many well - written stories about them. Just search for their names and you might find some great reads.