Hi espiritone,
The fist thing I would suggest is giving your new mattress some time because all new mattresses will go through an initial break in period and soften to some degree over the first 30 days or so. I would also make sure that your firmness issue is also because of the mattress and not anything that you are using over it (such as a mattress pad or a topper). It may also be worth reading post #2 here. I would suggest waiting a minimum of 2 weeks if possible.
Once you are past the break in period and if your mattress is still too firm … then a topper can be a good idea to soften a mattress that is too firm. You will find some topper guidelines in post #2 here that can help you make the best choice. Most people would tend to do best with a topper in the 2 - 3" range depending on how much extra pressure relief is needed and the other factors that are involved. In general … “just enough” is usually safer in terms of alignment.
Yes … the blended Talalay latex you will find ranges from 30% to 40% natural rubber (NR) and 60% - 70% synthetic rubber (SBR) and they are all good quality materials and the topper you are looking at is very good value as well.
If you mean a mattress protector then it’s probably a better idea to get the latex topper with the cover to protect it from ozone and ultraviolet light as well as other things which can cause it to oxidize and degrade prematurely. Latex needs a good cover rather than just a mattress protector to keep it in good condition over a longer period of time.
Phoenix