Hi nascarnole,
Regarding the latex in a latex hybrid mattress, as mentioned in the mattress durability guidelines listed at the beginning of this thread, any latex (Dunlop or Talalay – synthetic, blended or natural), would be considered a high quality material and unlikely to reduce the useful life of a hybrid mattress.
Both Dunlop and Talalay have their own unique comfort characteristics, and the differences between them are summarized in post #6 here. The preference of choosing one type over the other would be a personal, and not a quality, choice, and the ability to be able to test something similar in person (if ordering online) would be the best way to determine if you had an affinity for one version of the latex versus another.
Regarding the innerspring support unit, this would most often be some version of a pocketed spring unit in a latex hybrid mattress, and again this usually isn’t the “weak link” within a mattress. Some manufacturers will offer a few different pocketed spring options (often something adding zoning or perhaps a firmer spring unit) that they might recommend for different sleeping posture, BMIs or personal preferences.
The best advice I can provide when you can’t test a mattress in person is always a more detailed phone conversation with a knowledgeable and experienced retailer or manufacturer that has your best interests at heart and who can help “talk you through” the specifics of their mattresses and the properties and “feel” of the different latex materials and spring units and the options they have available that may be the best “match” for you based on the information you provide them, any local testing you have done or mattresses you have slept on and liked or other mattresses you are considering that they are familiar with, and the “averages” of other customers that are similar to you. They will know more about “matching” their specific mattress designs, options, and firmness levels to different body types, sleeping positions, and preferences (or to other mattresses that they are familiar with) than anyone else.
As for thickness, the thickness of a mattress is just a side effect of the design and by itself isn’t particularly meaningful because whether a thicker or thinner mattress would be better or worse for any particular person will depend on the specifics of the materials (type, firmness, etc.) and on all the other layers in the mattress. Thickness is only one of many specs that are used to make different mattresses that perform and feel differently and that makes a mattress suitable for one person and not another. There is more about the effect of thickness in post #14 here. Regardless of how thick or thin a mattress may be, the most important part of the “value” of a mattress is how suitable it is “as a whole” for your particular body type, sleeping positions, and preferences in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) regardless of how thick it may be.
I hope that helps makes things a bit easier to understand.
Phoenix