Hi KJEN,
You can read more about the differences between blended and 100% natural Talalay in post #2 here. They both have a sweet type of smell (like vanilla or sugar cookies).
There is more about the different types of latex in post #6 here and more about the differences between NR and SBR and some reference links in post #2 here.
Natural Dunlop will have more of a “rubber” smell that can be a little more persistant and will vary from product to product (like all natural materials).
Synthetic Dunlop doesn’t have what I would call a “chemical” smell at all (I just smelled a layer of mostly synthetic Dunlop that I own and the smell is very nondescript and you have to try hard to smell anything) but the smell of latex can can also vary by manufacturer and formulation.
Latex is a very durable material whether it is synthetic, blended, or 100% natural and for the most part they all have the same Oeko-Tex testing for VOC’s and harmful substances. As you mentioned natural rubber is more elastic and has a higher tear strength than SBR (synthetic rubber).
Phoenix