The amount of carbs being used over time will be determined by the individual’s intensity and economy/efficiency at using carbs. Hydration will be influenced by the environment and how the individual sweats, for example, a high salty sweater. This website/person is a very good place to start:
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I would not try to guess at or mix your own electrolyte replacement drinks. Either buy a commercially available drink that is meant for endurance sport or listen to your body. Also depends what is in the carbohydrates that you are consuming.
But yes, I would think that an amateur runner expends energy more slowly - but they will be on the course for longer.