Hi sgs006,
The first place I would start your research is the mattress shopping tutorial here which has all the basic information, steps, and guidelines that can help you make the best possible choices … and includes the answers to most of your questions as well.
Dreamfoam is one of the most discussed manufacturers on the forum and a forum search on Dreamfoam (you can just click the link) will bring up over 1500 posts that mention them. Forum searches on “ultimate dreams” or on any specific mattress you are considering will also bring up more information and feedback about them.
They are a sister company to Brooklyn Bedding (see post #4 here and post #3 here) and both of them are manufacturing members of this site which means that I think very highly of them and they compete well with the best in the industry in terms of their quality, value, service, and transparency.
Outside of all the information in the tutorial post … there is more about assessing the “value” of a mattress purchase in post #13 here that will be helpful.
The guidelines here can also help you assess the quality of the materials in a mattress relative to your budget range so you can identify any weak links in a mattress and make more meaningful comparisons to other mattresses.
They will provide you with any specific information you may need about the type and density of any of their base layers but for the most part their base foam is a firmer polyfoam that is 1.5 lb density.
This is a thinner layer of soft polyfoam that is used in quilting layers that is used to affect the surface “feel” of a mattress. There is more about quilting foam and other types of quilting materials in post #12 here.
If you like the feel and performance of Talalay latex and you are in a lower budget range then one of the Dreamfoam mattresses would certainly be well worth considering.
Phoenix