Nice introduction to the plotter / pantser topic! :)

I'm working on a novel at the moment, and it started very similar as to what you describe as your own process of a story evolving. With first a character and a setting and then a theme. I wrote the first draft just sitting and typing and enjoying the process of following the flow of ideas and expressing them in words.

After that first draft, I felt the storyline had potential, and wanted to improve on it. And found Jessica Brody's 15 beat story structure, and put it next to my own story arc. Having a more detailed framework on what to have where is now really helping me to get rhythm into my story. And in reorganising things, I feel things are improving big time. It's something I could recommend to other pantsers! :)