Hi kfinn,
There are links to some of the theory involved in matching a mattress to different body types and sleeping positions in mattress firmness/comfort levels in post #2 here but this is only generic information and not meant to be specific for any person. Outside of your own personal testing the best way to choose which of their configurations would be best for you would be a more detailed conversation with SleepEz. They are much more knowledgeable about their own mattresses and will be able to give you better guidance based on the averages of their customers than anyone else.
In terms of thickness 8" - 9" is a very common thickness and would be fine in some configuration for most people in normal weight ranges or even approaching the mid 200’s or higher. For lighter body types then even 6" of latex can also work well depending on the design of the mattress and the needs and preferences of the person sleeping on it.
Savvy Rest also makes a mattress that has either two, three, or four 3" layers of Talalay or Dunlop latex in your choice of firmness levels that you could test different configurations and they have some dealers near you that you can find on their dealer locator here.
The adjustable bed thread here has more information about adjustable beds and some sources you can use as a reference for “value”.
Phoenix