One common theme is Vash's struggle with his past. His actions in the past and the consequences they've had on him are often explored. Another theme is his relationships, like his friendship with other characters or potential romantic relationships. His pacifist beliefs are also a big theme, and how he tries to uphold them in different situations.
One great Vash the Stampede crossover fanfiction is the one where he crosses over with the Cowboy Bebop universe. It's really interesting to see how Vash's pacifist nature clashes and also meshes with the more morally ambiguous characters in Cowboy Bebop. The author does a great job of maintaining Vash's character while exploring new storylines in the Bebop world.
You can try some popular fanfiction websites like Archive of Our Own (AO3). It has a large collection of fanfictions related to various works, including Vash the Stampede. Just search for 'Vash the Stampede' in the search bar, and you'll get a bunch of results.
One popular trope is the 'fish out of water' trope. When Vash crosses over into another universe, he often has to adapt to new rules and cultures, which makes for some really fun and comical situations. For example, if he crosses into a modern - day Earth setting, his old - fashioned ways and his gun - slinging skills seem out of place but also really cool.
Overall, Trigun Stampede adheres closely to the manga. Some minor details might differ for the sake of the adaptation's flow and visual presentation, but the core remains the same.
Vash doesn't die. The manga's storyline keeps him alive through all the challenges and adventures. The creators chose to give him a different fate than death.
Definitely not. Vash is a figment of someone's creative mind. It has no roots in true events. The entire concept is built from scratch for the purpose of providing an enjoyable and imaginative experience for viewers and readers.