I typically do a good deal of my actual story planning on paper first. I would probably write a good deal more of my stories longhand too if it didn’t take so long.
In college I was around quite a few engineering majors who had piles of graphing paper. There was something about the way it could be used for notes, designs, and calculations without the sense of imposition that regular lined paper gave.
Then, I heard about bullet journaling and discovered the dot grid notebooks.
Both are now my preferred paper for story plotting and notes.
It gives me just enough to keep me linear if desired, without impeding my sense of freedom (though dot grid is a little better at this than standard graphing paper).