Hi Immi,
I would “echo” the great thoughts and suggestions that brass made … especially about sizing.
There are also a number of manufacturers in the list of online members here that make a range of component latex mattresses using different types and blends of latex.
Besides the 12 in 1 customizable … Dreamfoam also has their Freedom customizable latex mattress here which is a 3 x 3" layer component latex mattress that uses synthetic latex.
As Brass also mentioned … there are so many variables involved that it’s usually best to test different types of latex in different firmness levels in person to get a good idea of the combination that would be the best match for you in terms of PPP (see mattress firmness/comfort levels in post #2 here).
Phoenix