Hi Rob,
The specs for the Nature are listed in post #2 here.
There is no way for me to know whether any mattress would be suitable for a particular person based on specs (either theirs or a mattress) or theory because there are too many unknowns and variables involved that are unique to each person but I think that the Pamper, the Nature, and the Nutrition could all work well for “some” back sleepers (although not others) while the Beautiful or the WBB would be more risky choices (although they may also work for some because real life is often very different from “theory”).
There is no such thing as an “optimum set up” in general and again … there are too many unknowns and variables for me to know what an optimum set up would be for you until you have tried it. All I can reliably tell you based on your feedback and the reference points that you’ve provided is that the Etoile Pelushe clearly has comfort layers that are too thick and soft for you and that you would likely do better with thinner/firmer comfort layers.
I don’t know of any online manufacturers or suppliers that are using or sell the Graphite Talalay in individual layers and I also don’t know of any that have a stretch knit cover that is quilted with Talalay latex so the closest you could come would probably be to buy LI blended Talalay layers in the same thickness and firmness levels (KTT and Sleep Like a Bear both supply LI layers in all the firmness levels they have available), add an additional 1" of either 19 or 24 ILD blended Talalay on top (to “approximate” the quilted cover) and then put these inside a tight fitting stretch knit cover from one of the suppliers in the component list here (or in post #4 here).
No … they don’t sell to consumers … only manufacturers.
Phoenix