Hi Orchid,
There are a couple of versions of the Sequoia and one has an innerspring and one has latex with no innerspring. From what I can see though (such as here) the innerspring version is 11" thick not 9". In the end though it doesn’t make that much difference if you are choosing a topper based on where you are in the range from “just a touch” to “a lot” and tailoring your choices to your body type and sleeping style and what you are familiar with.
While Las Vegas is somewhat of a mattress desert in terms of local manufacturers … some of the better options and possibilities I’m aware of that may help you become a little more familiar with different types of latex are listed in post #2 here.
Phoenix