Typically, in Ash x Max yaoi fanfiction, there would be a focus on the relationship between Ash and Max. It might explore their emotions towards each other in a romantic or more intimate way. The stories could also play with their different personalities, with Ash's adventurous spirit and Max's perhaps more curious or in - some - versions - innocent nature.
One popular theme is adventure. Writers often send Ash, May, and Max on new Pokémon - related adventures that are not part of the original storyline. It could be exploring a new, uncharted region full of rare Pokémon.
Well, I'm not an expert in this specific yaoi fanfiction area. However, you can also check out some fanfiction forums where fans might discuss and share their favorite Ash x Max yaoi stories. Sometimes, they can give you great leads to find some interesting reads.
You can try fanfiction websites like FanFiction.net or Archive of Our Own. Just search for 'Ash and May Max' on their search bars, and you'll likely find a variety of fanfictions related to them. These platforms have a large collection of works created by fans from all over the world.
Well, you'd have to look at the details and the source. If there are no claims of it being true or references to real people and events, it's likely not a true story. However, some elements within it might have roots in reality.