One cup does seem like a bit much. The "standard" 5 oz (by weight) of dextrose carbs to about 2.4 volumes of CO2, which is sort of an average okay level for most beers. Different styles are traditionally carbonated to different levels. Wheat beers are carbed to 3-3.5 volumes and many British styles are carbed to 1-2 volumes. Books on recipe design such as Designing Great Beers by Ray Daniels get into this more. There are a calculators online and as part of various brewing software programs and apps to figure out how much of what type of sugar to add to get to what carbonation level.
"Chill haze is not a flaw."
Supersecret sour beer experiment
Battle Cruise Blonde Ale II