Hi truesdal,
I should clarify some terminology first just to make sure we are talking about the same thing.
A mattress cover (or ticking) is the material that is used to enclose your mattress and is part of the mattress itself. Is this what you are looking for and are you currently sleeping on the raw latex (with just your sheets and bedding over it)?
If this is the case then the type of cover is really a matter of personal preference but in general the choice will be between a thinner stretch knit cover and a quilted cover. There is more about the pros and cons of each in post #12 here and there is more about the pros and cons of a wool quilted cover in post #6 here. The better sources I’m aware of for mattress covers are listed in post #4 here and if you do decide on a thinner stretch knit cover then post #4 here lists the better sources I’m aware of that sell them.
If your mattress already has a mattress cover and all you are looking for is a mattress protector to protect your mattress from accidents and spills and the body fluids and oils that we release each night and to keep your sleeping surface in a clean and hygienic condition with the least possible effect on the mattress itself then post #89 here has more about the pros and cons of different types of mattress protectors.
A mattress pad is meant to add some additional softness to the mattress (it’s “in between” a protector and a topper in terms of thickness) and is used if your mattress needs some fine tuning and additional softness although some of them can also double up as a protector as well but in general a mattress pad is thicker than a mattress protector and will have a more significant effect on the feel of your mattress and it’s ability to contour to the shape of your body. There is more about mattress pads in post #10 here.
They won’t harm the latex so they can be a suitable choice for those that tend to sleep too cold and and more “passive” temperature regulating materials (such as wool) aren’t enough although they will also affect the “feel” of the latex underneath them to some degree.
Phoenix