Smoking/alcohol before Astral Projection

Yes, it will lower your vibrational frequency, which will either hinder you from projecting or if you still manage to project you'll be vulnerable to attacks and might see some unpleasant/scary things.

Ideally you shouldn't smoke and drink in the long run as well , but if it's too difficult for you try to make it occasional.

Also, if you're going to project, I recommend to not smoke and drink for at least 3 days prior the attempt.That will give you sometime to raise your vibrations.