From scene outline to completed fully-written first draft, my first book took me around two months of full-time writing.
It seems almost counter intuitive: Wouldn't it be faster to just go straight into writing the novel?
When I wrote my first novel, I sat down and prepared a rough plot outline. Then I broke the plot into a detailed scene outline. Following that, I expanded each scene into a couple of paragraphs.
This all sounds like a lot of work.
The benefit was that it laid down a strong foundation for me to write without distracting plot issues. When I began writing the dialogue and narrative, I didn't worry about what was going to happen next in the story because I had it all outlined. I could focus on writing the current scene and I knew exactly what would happen next, and where the story was leading to.
There's also another speed-related benefit of doing the outline. When I created the scene outline, if I wasn't happy with where it was going or I needed to increase the plot tension, I could revise the outline without having to re-write voluminous pages of narrative and dialogue.
And for that other question: Does a detailed outline limit your creativity? No, not at all. I was being creative when I prepared the plot. I was being creative when I outlined what happened in each and every scene outline. I was being creative when I wrote the dialogue and narrative, I was being creative in envisioning the scenes and committing it down into written word. No, your creativity will not be stifled. In fact, it frees your brain to be creative in a structured way (this will be a great subject for another post).
A detailed outline worked for me and I believe it'll work for you.