Well, you have to remember, there weren't radios, phones, and so on during this period, so, if a bunch of farmers wanted to collect their guns and go shoot at someone, no one could stop them!

In any case, "militias" (and the word is very vague, these people could basically end up as bandits, did sometimes operate without much oversight from nearby (If there were any) Continental army forces. This is especially true in the southern states, especially in Georgia and North Carolina.

While they did sometimes operate as an ad hoc force, they often operated alongside and underneath Continental Army regulars, often at pretty significant battles like Cowpens and Moore's Creek Bridge.

The British also made use of militia, both in an informal fashion in the backcountry, but also raising regiments of Loyalist militia, like The Royal North Carolina Regiment who were technically not militia, but essentially were.

So the answer to your question is an unsatisfying "it varied."