Hi fred33.
Welcome to our Mattress Forum! 
Currently this information is presented in various posts throughout the site, but your post prompted me to start some info consolidation so I’ll include here some the charts I worked on. You can also use the forum search tool for other details and matufacturers.
TALALAY
DUNLOP
Most Dunlop manufacturers list density, as this is more accurate metric for comparing than ILDs, because most Dunlop companies use a formula to predict ILD in Dunlop instead of actual measurements, which is why you can get a wide swing for ILD measurements in Dunlop. Here are a few Dunlop charts I put togheter. I’ll add more later as I have time.
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A side to side split as has the advantage that you can choose a different initial design and firmness level with different levels of comfort and/or support for each side of the mattress which can certainly be beneficial for couples that are in different weight ranges or that have different needs and preferences in a mattress. Having a side to side split also allows you to “fine tune” the comfort and/or support on each side of the mattress separately from the other side by rearranging layers or replacing a layer on one side of the mattress without affecting the other side and it also is a lot easier to assemble/disassemble a mattress using the split left and right sides, (and usually you won’t notice the seam where they meet in the middle.) There is more about the pros and cons of a split layer mattress in post #2 herepost #2 here. Also has more information about couples that have a larger weight differential
Engauge Frame is a good quality frame from Knickerbocker, less expensive, with a weight capacity of 2500 lbs, which comes with fiberglass tapered legs designer element. The slats aren’t meant to be used with the bed frame and you would certainly need a foundation.
The only way to know whether any specific mattress design or combination of layers and components is a good “match” for you in terms of comfort, firmness, and PPP with any certainty will be based on your own careful testing and/or your own personal experience when you sleep on it. It will also depend on your body type and sleeping positions as well because side sleepers may need more softness and contouring than back or prone sleepers. Having said that … you can see some general comments about the properties of an “ideal” mattress in post #4 here.
Post #14 here has more about the benefits of thicker comfort layers and thicker mattresses (most of these are in the tutorial post but I thought I’d highlight them here as well). Post #2 here has some generic guidelines for different body types and sleeping positions
When you can’t test a mattress in person then the most reliable source of guidance 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 materials they are using (resilience, firmness etc) 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 and firmness levels and the different options they have available to different body types, sleeping positions, and preferences or to other mattresses that they are familiar with than anyone else.
A good online retailer or manufacturer will generally make suggestions that they honestly believe have the best chance of success based on the information you provide them when you talk to them on the phone because this is in both your own and their best interests but once again … at the end of the day the only way to know for certain whether any specific mattress is a good match for you in terms of comfort, firmness, and PPP (or how it compares to another mattress) will be based on your own careful testing and/or your own personal experience so if you can’t test a specific mattress in person then the options you have available after a purchase to either exchange the mattress (or individual layers or components in some cases) or return the mattress for a refund (and any costs involved) would generally become a more important part of most people’s personal value equationjust in case a mattress you purchase doesn’t turn out as well as you hoped for.
It is always reccomended to use some sort of mattress pad or protector over your mattress (St…Dormeir is a good quality protector that many of our trusted members offer) Using a wool mattress pad over a mattress covering that contains some wool isn’t overkill – some people like the feel of wool , it will slightly modify the surface tension and feel of your mattress.
Designing and building your own mattress can be a lot of fun but can also be quite frustrating and involves a lot more knowledge of how different materials, layers, and components interact than many people suspect. Posts 15 - 17 here may be worth reading and I would normally recommend working closely with a manufacturer who will be able to give good advice about all the different components (option 2 in the linked post) over using your own knowledge and separate sources to build your mattress (option 3 in the linked post) but for those who want to forge ahead with their own design anyway … this will provide some options.
Good luck with your DIY!
Phoenix