I have done some testing with the AMNPS and the AMNTS and have found that both work well, but different.
The AMNPS smokes longer but not as heavy of a smoke. So, this is great to use when cold-smoking bacon or other long smokes.
The AMPTS is my favorite because it stays lit better and provides a heavier smoke albeit for a shorter time. I have a 6" and an 18" model and use both depending on how long I need to smoke for.
I documented my thoughts/testing on this in the following thread:
A-MAZE-N Cold Smoke Generator
I still really don't see much need for the A-MAZE-N smoker except for cold-smoking. For all other smokes I prefer to use chunk or chips. If you are going to use for a hot smoke, you'll need to come come up with some type of tent/cover to prevent drippings from dropping on the smoker. Or, if you get a #4, you will most likely have enough room to have the meat on one side of the smoker and the smoker on the other side.
For the tube, I remove my smoke box and rest the tube on the front of the smoke box frame and the back of the tube on the #3 element. This rests right about the drain hole where air can come in. Since I am cold smoking I remove my drip plate to allow for more air to get to the drain hole.
I had some trouble with my earlier tests, but I think it is because my mini-torch was not getting the pellets lit adequately enough. My kids got me a propane torch for Christmas a couple years ago and I have not had my A-MAZE-N smokers go out on me since.
I slight wind is necessary to get some air flow though. Otherwise others have used fish tank aeroators or even a James Jerky Dryer if you have one to keep air moving through the smoker. The A-MAZE-N going out on you is easily remedied with a few slight tweaks that do not require modifying your smoker.
I would think On the #4 it would be even easier since to keep lit since you have more air/space.