Hi E-Four,
The first comment I would make is that you could consider every mattress you are testing to be a “foam” mattress since it would be very uncommon to find a mattress that only used natural fibers in the comfort layers (such as wool or horsehair) which are the layers that you sleep on and “feel” the most. The question is really about what type of foam is used in the comfort layers (memory foam or it’s variant gel memory foam of various types, polyfoam, or latex foam). all of these have very different properties and there are many variations in each category. No matter what type of support layer you find in a mattress (innersprings, polyfoam. or latex are the most common) … you will generally be sleeping on some type of foam and possibly some type of fiber in the mattress quilting.
The first place I would start in your research is post #1 here and the information it links to which is the most important post on the forum when you are first starting to look for a mattress. This will give you all the basic information you need to know a bit more about mattresses and the materials inside them and avoid most of the worse choices of either mattresses or retailers that sell them (such as the major brands you are considering and chain stores) and focus on the better options and materials available to you. These can match all your needs and preferences (including temperature regulation) using much higher quality foams and components (better durability) at better prices (better “value”) than the major brands.
Some of the better options and possibilities in the Atlanta area are in post #2 here.
Phoenix