Some studios like short and simple, some like it more detailed. Personally, I love having a more detailed GDD. It helps to solidify the design of the game early, when mistakes are less costly. The deeper you get into development, the more expensive changes become.
https://www.boarsheadstudio.com/wp-content/uploads/2026/05/BH-GDD-Template.docx
Feel free to download and copy!