Great build
I feel your pain in working with aluminum sheet metal. I am curious what thickness did you use? It looks like I am going to help a friend build one. I used 0.040 on mine and I had to score every bend to make it work. It was a pain and I used up a new ferrous metal circular saw blade by the time I was done. It looks like your sheeting is a little thinner.
As far as smoke I have both an AMTS and a frying pan over my propane burner that I burn chunks. I use one or the other depending on what I am doing. The AMTS sure is easy and provides a consistent long burning smoke. I originally only had it for low temperature smoke but I find that I am using it more and more. Todd has a great selection of types of wood pellets and he has the best customer service in the business. Definitely worth looking at.
It looks like you have a pretty good airspace between your burner and the floor, but given
the pictures as S2K9K's fire I would probably opt for overkill and but some type ceramic tile covered with a sheet of aluminum directly under the burner. I have a propane burner on legs that is 6" off the floor but his pictures still made me take another close look at my build.
I look forward to hearing how your build smokes. I am sure that it is going to be great.