I'm definitely more of a Facilitator GM. The games I run are far from the stereotype of kids in a basement in wizard costumes. When I play its in a pub and generally quite casual. That's not to say we don't sometimes have groups with grid maps and miniatures but the majority of the time there isn't the room for high levels of prep to be brought.
One thing I have learnt from over prepping is that players will go out of their way to destroy anything you had planned anyway. You need to have light ideas that are flexible and can be reused if part of the story goes off tracks.
Have a general idea of what you want to accomplish in the session and see what happens.
On the other hand one shots differ from a campaign. In a one shot I will plan like a storyteller and make sure players feel like they got someone out of just the single session even if it was just an excuse to get drunk.
Storyteller – This is the GM who is crafting a story that they want the players to play through.They often construct this as a fairly linear plot that has an assumed finale. Narrator – The Narrator is a more relaxed Storyteller. They still have a story to tell and an ending in mind, but they have loosened on the linear plot and have adapted a more flexible, but finite set of scenes that can be executed in any order, but all lead to the assumed finale. Facilitator – This is the improvisational GM. They arrive at the game with only a slight idea of where the game will start and an intended direction, and they will then use the events and ideas at the table to drive a game to some conclusion, which is not often known before play starts.