Hi bubbles,
The first place I would start your research is the tutorial post here which has all the basic information, steps, and guidelines that can help you make the best possible choices that are most suitable for you and based on the criteria that are most important to you (regardless of whether the same criteria would be important for someone else). They will also help you learn how to avoid the worst choices and make more meaningful comparisons between mattresses.
Mattress “safety” is a complex question and each person may have their own answer to “how safe is safe enough for me?” depending on their circumstances and the choices they are most comfortable with on a personal basis. The comments I made to a similar question here yesterday and the other posts it links to would be the same way I would answer your questions about the “safety” of different materials as well.
The brand name on a mattress is not important because outside of careful and objective testing (using the testing guidelines in the tutorial post) to make sure a mattress is a good match for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) a mattress is only as good as the quality/durability of the materials inside it. The better options and possibilities I’m aware of in the Los Angeles region are listed in post #2 here.
This would depend entirely on how you define “best” and on your own personal preferences between materials and different types of mattresses. Any combination of materials or components can be used to make a mattress that is either a perfect match for you or a mattress that would be completely unsuitable for you to sleep on. The specific design of a mattress and how well it matches your specific needs and preferences is much more important than the type of materials. Every type of material has higher quality and more durable versions and lower quality less durable versions so regardless of the type of materials or components that your testing indicates is your preference … it’s always important to make sure that your mattress uses high quality durable materials relative to your budget range and that there are no weak links in the mattress in terms of durability.
As you can see in the guidelines here (also linked in the tutorial post) … Tempurpedic is one of the “major manufacturers” that I would avoid and there are many other memory foam mattresses that use the same quality/durability of materials that are in a much better budget range.
Wool allergies are generally contact allergies so it may be fine to include it as a quilting layer or an inner layer of your mattress where there is no contact but of course this would also depend on what you were comfortable with.
Keetsa is one of many Zinus Brands which is a Chinese manufacturer that tends to make mattresses that use memory foam in a low/mid range in terms of quality along with latex hybrid innerspring mattresses. They have a somewhat exaggerated focus on “green” mattresses which is somewhat odd considering that they use memory foam and polyfoam in their mattresses which certainly aren’t “green” or “natural” materials. A forum search on Keetsa (you can just click this) will bring up more information and feedback about them. There is also an analysis of the Saatva mattresses and their marketing claims in post #1 here and a forum search on Saatva (you can just click this as well) will also bring up more information about them.
Out of the two … which one is the best “value” for you would depend on the specific mattresses you were comparing (and the materials inside them) and the parts of your personal value equation that were most important to you but neither one would likely be my first choice compared to the many other options that are available to you.
The first part of post #2 here also has some information that may be helpful for couples that have very different needs and preferences.
Phoenix
PS: I switched your post to a new topic that included Keetsa and Saatva in the title so that they would be easier for others to find and not get mixed in with a topic about latex (neither of them make an all latex mattress and Saatva doesn’t use latex at all in any of their mattresses).