Luffy in the manga is strong, for sure. He's constantly evolving and unlocking new abilities. When compared to others, it depends on the context and the specific situation. Sometimes he might have an edge, while in other cases, his opponents could pose a significant challenge.
The main difference is the freedom in fanfiction. Writers can create scenarios where Naruto has access to more powerful mentors or discovers hidden powers within himself more quickly. For instance, he might find a way to fully merge with the Nine - Tails in a way that gives him god - like powers much earlier than in the original. This is all part of the creative license that fanfiction allows, making him seem much stronger compared to the original series.
Life can be like a novel because, just like in a novel, there are different chapters in life. Each stage, from childhood to old age, is like a chapter with its own story, characters (the people we meet), and plot twists (unexpected events).
The accuracy of fact versus fiction varies. Fact is based on verified information and observable truths. Fiction can range from being loosely inspired by real-life to being completely fantastical. Generally, when it comes to representing the real world, fact is more accurate.