"It feels like when using a vape PEN, I have much worse respiratory reactions – like severe coughing, wheezing, tightness of the chest, shortening of breath, "popping" or crackling sounds while breathing, and a few other symptoms. it seems less so with a water pipe, and I’ve recently read about ‘popcorn lung’ being related to vape pens. Is there any research or are there any experts who are looking into it?"
Can you give us any more history? Are you a smoker or have been in the past? How many years have you been using a water pipe? Are there any other associated symptoms? (i.e. night sweats, fevers) The term "popcorn lung" is formally know in medicine as a condition called bronchilitis obliterans. In the literature, the causative agent is thought to be an additive known as diacetyl. From what I’ve looked up, this agent is more found in e-cigarettes because it is a flavoring agent. I can’t speak for vape-pens because I need to do more research on the subject but I know that more and more companies are self-regulating their products because of concerns of this nature.
A few more points; "popcorn lung" has so many other features related to chronic obstructive pulmonary disease (COPD) which includes obstructive asthma and emphysema. My advice? Stop inhalation products altogether and see an MD, maybe consider a chest x-ray. I hope this helps, please let us know what you do