Hi Shonya,
I’m not sure what materials you are able to tolerate and this is a complex subject with issues like autoimmune diseases and MCS (multiple chemical sensitivities) so you would know more than I would about the materials you can tolerate because it’s very individual. Some people don’t do as well with some materials and others do better. As a group … memory foam is usually the least well tolerated and polyfoam is “iffy” depending on the person.
Post #4 here has more information about natural materials that you may do better with but they boil down to natural fibers, latex, and innersprings. You may find an innerspring latex hybrid mattress inside your budget and many pocket coils are fine with adjustable beds. Other innersprings that don’t have a border wire or are specially made to flex with an adjustable bed are also OK. It’s important to make sure that the manufacturer or retailer knows that you are planning to use your mattress with an adjustable bed so that they only show you the ones that are suitable. It may also be worth considering a mattress that doesn’t contain any fire retardants which are available with a prescription from a health professional (and you don’t get charged tax either with a prescription). The size of mattress you are looking for will also play a major role in your budget and larger sizes are of course more costly.
As far as comfort that’s such an individual matter that your own testing will be the most important part of your choice. In general though if you have progressively firmer layers then the transition between the layers will be much more gradual than if you have a very soft layer over a very firm layer. Rather than getting into more technical details though it’s usually best to either trust your own personal testing or if you are considering an online purchase then a more detailed conversation on the phone that includes as much detail about your criteria as possible will help them give you3better suggestions.
With the local manufacturers or retailers on the lists I linked I would spend some time on the phone with them first telling them more specifics about what you are looking for so you can get a better sense of what they have available and their level of knowledge and service and how well you “connect” with them before you go there. this can save you a lot of time and travel.
Phoenix