I take NAC in capsules. There is all kinds of speculation about effectiveness, but here are my observations:
I ran out when I couldn't get Jarrow brand - my muscles ached more, my hands were more swollen (arthritis) and my mucus got "stringy" again.
Then I found "NOW" brand and restarted - all of these settled down.
Just to check if it was still effective, I stopped for 10 days this past spring - same result.
I have also thought "do I need both" and stopped Mucinex - no effect on aches and pains, but my mucus got thicker and I got fluid behind the eardrum in my chronically bad ear.

So, for me the capsules work, and it's not one more thing I have to inhale.
Sue