Hi kismet,
The first place I would start is post #1 here which along with the information and guidelines it links to will help you eliminate most of your worse choices (such as the major brands you have been considering) and focus more on your better options. These are usually mattresses made by smaller local or independent manufacturers that are either sold factory direct or through better sleep shops which tend to have much higher quality materials and better value.
The easiest way to cut through the confusion is to work with “mattress people” who already know what you would otherwise need to learn and have your best interests at heart. One of the most reliable signs of these types of manufacturers or retailers are the ones who will provide you with the quality details of every layer in any mattress you are considering.
Both wool and latex in a mattress are generally covered by other materials so with contact allergies they may still be fine in a mattress. Your personal testing will usually tell you if there is any reason to be concerned. In addition to this … latex allergies are usually to the surface proteins of the latex which are mostly washed off during the manufacturing of latex foam (unlike latex gloves, condoms, or other solid rubber products). You may have read this but there is more about latex allergies in post #2 here which may help relieve most of your latex allergy concerns.
Some of the better options and possibilities in the Greenville area are listed in post #2 here. While the members here are certainly among the best quality and value in the country (and it would be well worth a reasonable drive in most cases to visit them) … there are also many other manufacturers who are not members here who make and/or sell high quality and value mattresses in and around most areas of the country including Greenville.
Hope this helps.
Phoenix