Hi landale1,
Welcome to the Mattress Forum! 
The Leggett and Platt {url=Error 404: Not Found - L&P Bedding Group]Quantum Edge Combi-Zone[/url] does use different zones, different gauges of steel, and different diameters of springs. In the Arizona Premium Ultimate Hybrid, the perimeter edge springs are 16 gauge steel. The middle third springs are 17 gauge, and the outer third (head and foot) springs are 14 gauge. The diameter of the springs along the edge and in the center third of the innerspring unit are similar to each other and smaller in diameter as compared to the springs at the head and the foot of the innerspring unit. The manipulation of the gauge of steel and the number/diameter/concentration of the springs allows the innerspring designers in this instance to produce a unit that allows for better support in the middle third of the mattress (through a higher spring concentration) but still allows for good conformation. The springs are a larger diameter at the head and foot zones (so the spring concentration in this area is not as great), so in order to still provide for good support the designers made these springs out of a bit thicker steel.
The My Green Mattress uses a Leggett and Platt Bolsa spring unit where there is a “nested” center third region. The springs are all similar in diameter, so in order to provide a bit more support in the center third, the springs are made out of 14.5 gauge steel, as opposed to 15.5 gauge steel at the head and foot of the mattress.
Both innerspring units are zoned and do provide more support in the middle third of the product, but they are engineered to go about it in different ways. Various zoning systems can also be very useful and worth considering for people who have more challenging circumstances or sensitivities, body types that are more difficult to “match” to a mattress, more complex medical issues, or who have a history of having more difficulty in finding a mattress that works well for them. There is more about zoning in this article and in post #11 here. Also in post #2 here and post #7 here (latex momzone unique properties).
Both Arizona Premium and My Green Mattress are members of this site which means that I think very highly of them and that I believe that they compete well with the best in the industry in terms of their quality, value, service, knowledge, and transparency. They are extremely knowledgeable about latex, hybrids and different configurations, and I would not hesitate to recommend either of them for your consideration.
There are many examples of mattresses using memory foam layers directly upon pocketed spring units. Sometimes a layer of poly foam is placed between the memory foam and the spring unit, as memory foam isn’t very resilient and is very point elastic, and depending upon the thickness and style of memory foam being used, the spring unit could be “felt through” the memory foam layer. Whether you chose to use latex, memory foam or polyfoam would be a personal preference, and you’d want to make sure that whatever type of foam you chose was a good density/quality.
If you have other questions, I’ll do my best to answer them.
Phoenix