Speaking from my pretty thorough experiments with NAC:
It did not help my anxiety at all whatsoever, it actually made it a lot worse in the end. If you take it daily, it acts as a potent mood stabilizer and dopamine modulator (sort of like an antipsychotic). It seems to be quite good for bipolar. It blocks depressive lows, but also blocks the happy highs, it blocks the euphoria from dopaminergic drugs such as nicotine, amphetamines, meth, other stimulants, certain opioids, etc.
If you want to use it for it's health benefits as an antioxidant and lung cleaner and stuff, just take a big dose for 1 day, maybe 2 or 3 if you have an illness. That's all you really need.
When you take it daily it starts acting much more like a psychiatric drug than an antioxidant.
After taking it for a few weeks, it gave me EXTREME anxiety reactions to common supplements and drugs, very very strange, and very uncomfortable. It also made me feel anhedonic for over a month after I stopped taking it.