What a 001 is differs from person to person. Out of universe, they're typically an author's "magnum opus", a piece that emphasizes their unique style and skill as an author. They're also normally fairly grand as a result, as they're often an author bringing out their very best to show off what they can do.
That said, there are plenty that aren't world-ending nightmares. Rounderhouse's Amoni-Ram is a worldbuilding story as much as it is a character study. Plague's proposal is very humble, focusing rather on the creative process with absolutely no world ending stakes. Ralliston's proposal is designed as a starting point for his canon and providing lore behind his setting.
So, in short, what a 001 is depends on the author. I recommend reading more than just the most popular ones, because that will help challenge your perception of what a 001 is.
