There seems to be quite a lot of chemistry happening in juice-mixing/steeping which is not fully understood yet. I guess that's fair, science doesn't have a huge knowledge database on liquids which are vaporised and then inhaled. Even the diversity of opinion on what we taste in vapour flavourings defies belief at times. Hopefully we can find answers to these things and steps can be taken to reduce harshness, off-flavours, throat hit, pepper, etc.