OK based on what I've read, a long trail drive such as one from Texas to Kansas had one chuckwagon per herd. They found out real quick to keep the herds down to maybe 2000 at most. If needed send a second crew and herd. The trail crew most often had around 11 men, 8 trail drivers which were 2 point, 4 swing and 2 drag, add a cook, a horse wrangler and the trail boss that's 11. One cook and chuck wagon could handle that pretty well.
They tried to keep a distance of several miles between herds. However these herds sometimes got mixed in a stampeed or at a flooded crossing. Then with a larger group of men to feed two or more wagons would gather together.
The same on round-ups, each outfit was expected to send hands and the wagon. Depending on terain, they might make one large camp with each cook doing the type of food they did best or the wagons might be more spread out and you were expected to eat at the wagon you were in the area of.