Hi Jacks,
Welcome back!
Overall, the best advice I can give to you is to go back and reread the mattress shopping tutorial. It points to information that will answer almost every questions you posed here. But I can help with some specifics.
As you like sleeping “on” a mattress rather than “in” it, you may prefer something that uses a firmer surface comfort material, either firmer polyfoam that uses a better density (1.8 ln or above), firmer latex, microcoils, or a combination of the above. You may also prefer a stronger innerspring unit versus a polyfoam core, as you stated you had an affinity for hotel mattresses, and in general these tend to be firmer products with less padding (usually firmer polyfoam) with some sort of a top-of-bed product attached on top (as you stated). Also, polyfoam and latex, in firmer versions, will tend to be more breathable and sleep “cooler” than memory foam.
With certifications, at a minimum for polyfoam you’d want a CertiPUR-US certification, and most latex you’re likely to come across will have some sort of a safety certification, such as Oek-Tex or eco institut.
If you’re planning on using a mattress on an adjustable bed base and you choose an innerspring product, those items using pocketed springs are the most common presently that are being made as “adjustable bed friendly”. All-latex mattresses can be used on adjustable beds, as well as latex mattresses using a polyfoam support core or ones using a pocketed spring support core.
Choosing a king or two twin extra long units would be a personal preference. If choosing adjustable beds, having two twin extra long mattresses would allow each person to individualize their elevation independent of the other.
Your other choices of not being made in China, exchanges, refunds and pricing would all be things to check when you are investigating the web sites of brands you are considering as part of your personal value equation.
If you’re shopping again online, you may wish to begin and use the experience and expertise of the members listed in post #21 here who are all very experienced and knowledgeable and specialize in providing the type of help and guidance on the phone that can help you make good choices. There are a wide range of latex and other options included in the choices there and I believe that all of them compete well with the best in the industry in terms of their quality, value, service, and transparency.
If you have more specific questions after reading through this material, consulting with manufacturers or testing out items locally, I’ll do my best to be of assistance.
Phoenix