Hi KarenLeePA,
You’re welcome!
The latex used in this mattress is Dunlop, but there isn’t complete information about the blend or certification information about this foam. There is a 7" polyfoam core beneath it but the density is unknown, so this is not an all-latex mattress. A forum search on Lucid (you can just click the link) will bring up comments and feedback about them. As you stated, Lucid is from China, and post #6 here is about mattresses imported from Asia or China which may have been compressed for long periods of time in either shipping or storage before being purchased, which in my opinion makes this a more risky purchase.
This mattress is also a polyfoam core product with latex on top. The 1.8 lb polyfoam core is 6" with a convolute on top and is topped by 3" of Talalay latex that can be custom-ordered in different ILDs (levels of firmness). The top quilt panel has 1.5" of a plush polyfoam quilted to the covering. As you may be aware, Dreamfoam is a site member here, which means that I think highly of them and their advice, and I feel they compete with the best in the industry in terms of guidance, product and quality. You’d want to place a phone call with Dreamfoam before placing any potential order, so as to receive their advice as to the plushness level that they would recommend for you. You are correct, you may not need a topper, and I would recommend you choose your mattress comfort level based upon attempting to find a plushness that would work for you, sans topper.
The Casper mattress contains no latex. You may be confusing it with the old specifications it had. You can see more about the Casper mattress specifications in the Simplified Choice Thread here.
Comfort Layers:
1.5" 3.5 lb ventilated polyfoam
1.5" 4 lb 10 ILD Memory foam
1.5" 2.5 lb polyfoam
Support Layers:
5" 1.5 lb 36 ILD Polyfoam
None of the mattresses you’re listing contain innersprings – they all have polyfoam support cores. And the Geo-Matt is a piece of polyfoam with some engineered (cut out) contours, so frequent replacement as you described you’re experiencing would be normal for that.
As for toppers, there is more information about choosing a topper in post #2 here and the topper guidelines it links to. There is more complete information there as well about choosing a latex topper. I believe this may the post you stated you had once read but were having a hard time finding again? Maybe not.
As far as picking a mattress for someone else, there are simply too many unknowns, variables, and personal preferences involved in choosing a mattress for someone else to make specific suggestions based on specs (either yours or a mattress) or theory at a distance that can possible be more accurate than your own careful and objective testing (using the testing guidelines in the tutorial post) which is always the most reliable way to predict which mattress will be the best match for you in terms of PPP (see mattress firmness/comfort levels in post #2 here).
Also, there are also no “standard” definitions or consensus of opinions for firmness ratings and different manufacturers can rate their mattresses very differently than others so a mattress that one manufacturer rates as being a specific firmness could be rated very differently by another manufacturer. Different people can also have very different perceptions of firmness and softness compared to others as well and a mattress that feels firm for one person can feel like “medium” for someone else or even “soft” for someone else (or vice versa) depending on their body type, sleeping style, physiology, their frame of reference based on what they are used to, and their individual sensitivity and perceptions. There are also different types of firmness and softness that different people may be sensitive to that can affect how they “rate” a mattress as well (see post #15 here) so different people can also have very different opinions on how two mattresses compare in terms of firmness and some people may rate one mattress as being firmer than another and someone else may rate them the other way around. This is all relative and very subjective and is as much an art as a science.
I know that is a bit of information, but I hope it begins to help you sort things out. If you read through this and come up with more specific questions, please post back and I’ll do my best to answer them for you.
Phoenix