Hi llylesmith,
I don’t know of any of their mattresses that only have 1 1/2" of latex but they do have models with either 3", 6", or 9" of latex. some of these have the ability to exchange one or more layers after a purchase if your comfort choice isn’t ideal for your specific needs and preferences.
You can see some of my thoughts about a latex/polyfoam hybrid vs an all latex mattress in post #2 here.
“Feel” is very subjective and varies by body type, sleeping positions, and personal perceptions but the closer to the top of a mattress a layer or component is the more it will contribute to the overall “feel” of the mattress for most (but not all) people. In general the comfort and transition layers of a mattress (top 3" - 6" or so) will be most of what people “feel” initially and the deeper layers (transition and support layers) will play a more important role in how they feel in the morning when they wake up. People who are higher weights or sleep in positions that are more pressure prone (such as side sleepers) and tend to sink deeper into a mattress will feel more of the deeper layers than those who are lighter or sleep in positions that have more surface area and are less prone to sinking in and pressure points (such as back and stomach sleepers).
Phoenix