Yes, the distinction between the volunteer militia companies, and the general militia, is an important one. The volunteer militia company usually numbered 40 or so men, who with ex-members returning to duty to could be mustered in to Confederate service virtually intact. They were much more prevalent in urban counties than strictly rural counties, for obvious reasons.
The general militia mostly was a military dud for CW purposes. I'm currently transcribing a diary of a man who lived in Memphis in 1861, and pronounced the militia election there a flat failure.