It's hard to say for sure. The availability of Venti in the story depends on multiple factors such as the story's genre, setting, and the author's intentions. It could be possible, but you'd have to look closely at the story's details to know for sure.
Yes, you can get Venti from the story. In the game's story, Venti is a key character. His story is intertwined with the lore of Mondstadt. For example, his role as the Anemo Archon is revealed through various quests. These quests show his connection to the city, its people, and the overall history of the region. He has a carefree yet mysterious personality, and his actions in the story often have a significant impact on the events that unfold in Mondstadt.
Well, in a Venti identity reveal fanfic, it could involve Venti dropping his carefree bard facade and showing his more divine or ancient side. It might include scenes where he has to use his true powers to protect Mondstadt from a great threat. And this could lead to a whole new understanding of his character by the people of Mondstadt and the readers of the fanfic.
Another possibility is that it could be a normal citizen of Mondstadt who has a special connection or intuition. This person might not be as powerful or important as Jean or Diluc, but they could have a moment of realization. Maybe they see Venti do something that defies normal human capabilities and start to suspect that there is more to him than meets the eye.
One characteristic is the exploration of their different personalities. Xiao is often portrayed as reserved and mysterious, while Lumine is more open - minded and curious. Their fanfics usually play with these traits in their interactions.