I’m a runner also...depends what you mean by long distances, but I’d promote becoming fat adapted and running in ketosis.

I’ve done a full marathon with no fuel (hydration only) in ketosis, pretty awesome and much better than my glucose/gu runs...of course I’ve had some amazing long runs out of ketosis but at certain distances the fueling is a real battle and a battle I’ve lost from time to time. I don’t think there is a good answer for fueling long distances that will work for everyone it’s all about personal experimentation and adaptation.