IME water has a diminutive effect on the vapor if any effect, as far as getting the full dose. It does create slight restriction when inhaling which I find beneficial. Without  water the heat may start to melt the plastic bottle where the end of the stem end is located.

I have never seen the glass vapor genie in any any heads shops in my area. I did see a classic once. Also none of the employees  talked to were even aware of its existence.

From the videos I watched before I got my gvg It didn't seem to produce very good vapor for Marijuana. It def works much better for DMT.