Hi Rosey,
Unlike memory foam and polyfoam where the foam density is the single biggest factor in durability … the density of latex is related to its firmness but not to the quality or durability of the material. Different types and blends of latex will have different density ranges (softer or firmer) or ILD ranges (ILD is a firmness rating) but with careful testing your body will tell you whether a mattress is a good match for you in terms of comfort, firmness, and PPP regardless of whether you know the density or firmness of the latex layers so I wouldn’t get caught up with the density or firmness of the individual layers because it may do more to confuse you than help you. There is more about the different types and blends of latex in post #7 here.
Phoenix