Hi Kiki,
If you can’t test a mattress in person then the best way to decide on whether any of the options they have available have a good chance of working well for you would be based on a more detailed conversation on the phone (see mattress firmness/comfort levels in post #2 here). They will know more about their mattresses and comfort options and “matching” their mattresses to different people than anyone else and will be in the best position to give you good guidance about their mattresses and the choices they have available.
I own one of their Lanoodles toppers (you can see my comments here and here) and I haven’t noticed any issues with it shifting (I use it under my mattress protector and a fitted sheet).
You can read more about the different types and blends of latex in post #6 here but all of the latex you are likely to encounter (Dunlop or Talalay made with either synthetic rubber, natural rubber, or a blend of the two) would be “safe” and are tested for harmful substances and VOC’s using the same or very similar testing protocols (either Oeko-Tex or Eco-Institut). I don’t think that most people (although there are always exceptions to every “rule”) would have any issues with safety or being able to tolerate any type of latex even with MCS.
While I’m always happy to help provide any information that can help with “how” to choose, answer questions about the properties or quality of different materials, to act as a “fact check”, and help eliminate the worst options … once you are down to all “good” options or final choices your choices become a preference issue so I leave the specifics of comfort choices, which mattress to choose, or which manufacturer or retailer to deal with up to each person and the results of their conversations with each of them. I would definitely suggest spending time on the phone with the ones you are attracted to that are included in the list of the online members here that are linked in the tutorial post and then use the information on their sites and the results of your more detailed conversations with each of them to decide which ones you believe would be the best “match” for you in terms of PPP and the parts of your personal value equation that are most important to you. I wouldn’t hesitate to deal with or make a purchase from any of them that I thought would work well for me.
If you let me know your city or zip code I’d also be happy to let you know about any of the better options or possibilities I’m aware of that are local to you so you can also use your own personal testing and experience as a reference point to help you decide.
Phoenix