Re: the tough stuff
I think of narghiles as basically an engine in that the vaporized liquid that you smoke is cycled through the smoke chamber in much the same way that gasses are cycled through a combustion chamber. I wrote something about that recently when people were talking about Egyptian and Syrian rigs.
All the parts matter. As does the height and with of the smoke column, the purge valves and diffusers (sometimes they are built into the smoke chamber) and a bunch of other stuff. It would be easier to answer you if get a bit more specific about what you want to know about.
Still, the truth is that the best narghile in the world with greatest moassel ever made will taste like crap if you don't use good coals, pack the bowl right for what you smoke and have good heat management.