Hi mtnhigh,
There are many factors involved in durability (which you can read about in post #4 here) so it would depend on the other durability factors that are involved. In an otherwise apples to apples comparison of blended Talalay vs 100% natural Talalay in lower ILD’s (not all ILD’s) though … then yes the blended would likely be more durable. You can read more about the difference between them in post #4 here. You can also read more about the different types of latex in post #2 here.
There is lots of generic information about layering and different body types and mattress designs in the Putting the layers together and in the Sleeping style, preferences, and statistics sections of the site as well as in the tips and tricks page here for those who are interested in some of the theory behind different designs and layering but I leave all the specific suggestions to more detailed conversations between you and the manufacturers or retailers you are dealing with. They are the experts with their own mattresses.
You can read more about foundations in the foundation thread here. In general a latex mattress does best with a firm non flexing foundation with gaps between the slats of 3" or less. In general though I would tend to follow the suggestions of each manufacturer regarding a foundation.
You can read more about the differences between a latex/polyfoam hybrid and an all latex mattress in post #2 here.
Phoenix
Phoenix