As you can see in the foam quality/density guidelines here … the 2" of 3 lb memory foam would certainly be a weak link in this mattress … and there should be many better options available in this price range. I personally wouldn’t consider it even for normal weight ranges and certainly not in weight ranges above about 200 lbs where I would start to reduce or minimize the use of 4 lb memory foam as well. These types of specs would be typical of Zinus which is a Chinese manufacturer which makes a wide range of memory foam mattresses under many different names including Night Therapy, Spirit Sleep, Enso, Vivon, Keetsa and others. A forum search on Zinus (you can just click the link) will bring up more information and feedback about them.
I would want to clarify the top 1.5" layer and confirm the type of material and the density (it has two densities listed) and I would also want to know the type and blend of the latex but overall these aren’t specs I would be comfortable with or consider either … especially with 3.5" of 1.2 lb polyfoam so close to the top surface.
There is more about the most important parts of the “value” of a mattress purchase in post #13 here but I would avoid both of these for durability reasons … especially at your weight … no matter how they felt in a showroom.