Re: diffuser, yes or no?
I seriously cannot tell the difference in the "smoothness" or "thickness" of the smoke with it on. What it will do is create a "smoother flow" on hookahs that would normally produce bigger bubbles that actually can be felt in the draw as they are created and released from the stem in the bottom. I might have to do vid on this to show that with the same bowl and same coals you will not get the smoke to change at all. If the smoke is cooler, id say only marginally, and well, theres always colder water that could do it for you.
I have quite a few, but honestly, I feel like its mostly a gimmick. If you dont want your hookah to be so loud, I get it. If you have an unstable hookah and the rumble makes the coals move around, I also get it. But putting it on each rig every time you smoke because its somehow a better smoke....not so much.