Both.
There are two different ways I write books.
One is the long gestation book, the book built off of themes I’ve been thinking of for years. I first wrote Dalinar (by a different name back then) in a story when I was a teenager. Same for Hoid. I wasn’t ready to write the story yet, as I wasn’t good enough, so I backed off.
Other books are almost more like performance art–you take a few ideas, you juggle them about a bit, and you then stand up on stage and do your best with them. In the hands of a skilled writer, this comes out like a solo from an improvisation expert. Flawed in places, yes, but also full of a kind of majestic life.
Some things work better in the first form. (Foreshadowing being one, carrying a story across multiple books is another.) Other things work better in the second. (Humor, for example.) Mostly, they just have a different feel.
The Way of Kings and Mistborn were like the first. Warbreaker and Alcatraz were like the second.
On Outlining
I do outline quite extensively. Remember, however, that authors each tend to do things their own ways. There’s no one perfect way to do this. George R. R. Martin described some of the extremes in terms of “Gardeners” and “Architects.” Gardeners grow a story, without a firm idea of where they are going. Architects tend to build an outline as a frame and work from it.
I’m (usually) an architect. I’ve found that the best way to get the kinds of endings I like. I have to know where I’m going before I start.
That said, an outline has to be a living thing of its own. I need the flexibility to knock out entire sections of it and rebuild them; I do that frequently. I have to be able to respond to what I’m passionate about in the world, as you mention. In the Stormlight books, the interludes were more reactionary, and I built them into the story to allow myself more freedom to explore the world in a “Gardener” sort of way, while the plot itself was quite well set out.