Hi flybear,
The topper guidelines in post #8 here may also be useful.
The choice between Talalay and Dunlop is strictly personal preference and some will prefer the feel of one and some the other. Post #7 here may give you some sense of the differences between them but personal testing is really the best way to know which one you prefer.
I also agree with dn that a cover is a good idea to extend the life of the latex. Ozone and ultraviolet light are two of the “enemies” of latex and can cause it to oxidize and break down prematurely.
Phoenix