A single sheet of paper for a seven book series doesn't sound too macro, especially given how Smith describes obsessing over details. Compare with Straczinski, who had a whole binder of note cards outlining the 5-year story arc of Babylon 5. Granted, TV show, not novel, but it felt more novel-like.
Rowling sounds more pantsy, like saying "I'm going to drive from SF to NYC, and I'm going to stop at my parents' in Denver", then when the day arrives, you sit in the car, pull up Apple Maps, and say, "hmm, I think I want to go the Las Vegas to Denver route rather than Salt Lake City, because it's winter", and then start driving and find a hotel when you're tired. Snow in Utah? Hmm, should I risk it or stop early? As opposed to planning it all out two weeks before, "Day 1: SF to LV, stay at Bellagio; Day 2: LV to Canyonlands NP, camp overnight; Day 3: Go hiking, weather permitting; Day 4: Canyonlands to Denver; ..."
I think it was here on HN many years ago someone mentioned they "plan the mountains, pants the valleys", which I think beautifully encapsulates the process (at least very similar to how I do it).
I'm primarly a pantser, but I have some basic skeleton framework of a plot. And I usually don't have any idea how A will connect to B and then to C until I'm in the moment writing.
Rowling sounds more pantsy, like saying "I'm going to drive from SF to NYC, and I'm going to stop at my parents' in Denver", then when the day arrives, you sit in the car, pull up Apple Maps, and say, "hmm, I think I want to go the Las Vegas to Denver route rather than Salt Lake City, because it's winter", and then start driving and find a hotel when you're tired. Snow in Utah? Hmm, should I risk it or stop early? As opposed to planning it all out two weeks before, "Day 1: SF to LV, stay at Bellagio; Day 2: LV to Canyonlands NP, camp overnight; Day 3: Go hiking, weather permitting; Day 4: Canyonlands to Denver; ..."