I did research the subject quite a lot, for what an non health pro or student can find, including NHS reports. The issue is that opinions evolve. Some high grade doctors were publicly against, then suddenly change, but with a bit of marketing agenda behind.

I wanted to cross check with ecigs "nerd" communities, who are fine grained in their approach of products and spend time discussing issues and qualities of liquids, and devices (combustion properties control matters).

I'm still looking for data about vaporizers (be it water + nicotine, or even THC).