Hi richtj99,
Welcome to the Mattress Forum! 
Atlantic Beds hasn’t been discussed too often here on the site, but that just indicates that fewer members have asked about them or have considered them (it’s not a pro or con issue). You may have come across this already, but the listing of site members also contains many sources for latex mattresses that I’m aware of that would also be worth considering.
When choosing something online, it’s important to deal with experienced, educated and helpful manufacturers who have the knowledge to guide you through the process and find something that they honestly think will fit your specific sleeping positions, somatotype, BMI and individual needs. Post #2 here and this topic have more about the pros and cons of a local vs an online purchase.
Whether or not a mattress is a “popular seller” wouldn’t be a reason that would dictate the appropriateness of an item for your specific demands, and I wouldn’t consider that an important fact to consider when making a purchase.
Atlantic Beds does make a couple of claims on their site that I don’t consider to be accurate. The first is about shipping a mattress compressed and you can see my thoughts about this in post #2 here. The second is about the benefits of component mattresses (usually with latex mattresses) vs glued layers and they indicate that component mattresses can have issues with layers shifting which isn’t normally the case (and is more about their marketing in their own self interest than reality). There is more about glued vs unglued layers in post #2 here and the post it links to. Post #2 here has some comments about them as well.
Unfortunately, they don’t offer complete details about the layers within the Insignia, only that is has 6" of “Smart Latex”, on top of two layers of polyfoam totaling 6". You’d want to know the type of latex (Dunlop or Talalay), the mixture (synthetic, natural or blended) and the ILD of that layer and if it is offered in multiple ILDs (softnesses). Then you’d want to learn of the thickness and density of the polyfoam layers beneath the latex. If you find out that information from them, feel free to post it back here and I’ll be happy to comment upon it for you.
“Smart latex” in the past was just a trade name for a mostly synthetic Dunlop latex made with a continuous pour process and manufactured by Mountaintop foam which made the Dunlop latex for Sealy and Stearns & Foster mattresses. It used inserts in the latex which create firmer and softer areas which is why they call it “smart”. While it’s still a good quality and durable material, it’s basically just synthetic Dunlop latex which is the lowest cost version of latex (which is still a good quality material). I’m not sure if what is contained in the Insignia is this same latex.
As for different sleeping positions, here is an article you might find interesting. The ability to incline the upper torso in an adjustable bed does provide relief for many suffering from GERD.
If you’re able to find out the information I mentioned previously and post back here, I’ll be happy to provide more commentary on what you’ve found.
Phoenix