I can't find it in the manual, but as long as they are in a stack then medics, corps and balloons work for the entire force right? or do any or all of them have to remain under a generals command?
Generals do not influence medic and baloons bonuses. You can see this by hovering with your mouse over envelope to see command points status, and by hovering over your units cohesion bar to see cohesion recovery rate.