Hi austintxsleeper,
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 … and avoid the worst ones (including major brands or any mattress where you aren’t able to find out the specifics of the materials inside it)
The better options and possibilities I’m aware of in the Austin area are listed in post #2 here.
A mattress is only as good as its construction and the materials inside it so outside of testing a mattress for PPP … the most important part of any mattress purchase is making sure that you know the quality of all the layers and materials inside the mattress.
If you can find out the specific information about the Sherwood you need to make an informed buying decision (the thickness of each layer from top to bottom, the type and density of any polyfoam or memory foam, and the type and blend of any latex especially) and post it on the forum I’d be happy to make more comments about it or help youy identify any weak link in the mattress.
It’s not likely you will be able to find out the information you would need about the Sealy but they generally use lower quality/density materials and I would tend to pass them by unless you are willing to make a blind purchase where the odds are high that you are buying lower quality materials which will soften and break down faster than the higher quality materials that are used by many smaller manufacturers.
I’m not so sure that most people would call either one “toxic” but if you are more sensitive than most or have a medical condition such as MCS (multiple chemical sensitivity) or other reasons to avoid substances or materials that most people would call safe then it can be a real challenge to make some of the very difficult lifestyle changes that can be involved in eliminating chemicals from your home including in your mattress. In these types of cases post #2 here and the links to other posts and sources of information it includes can be a good place to begin to help you sort through some of the complex, contradictory, and misleading information that can help you answer the question of “how safe is safe enough for me?” when it comes to a mattress.
Phoenix