I live in the Blue Ridge Mountains of western Virginia (as opposed to the state of West Virginia). I have to agree with Ensiform that I have heard all of these forms (and more), but I do need to add some minor commentary.
If a store advertisement says, "Y'all come back, now!" they are using this in the plural. They wish to have more than one future customer. Bring your kith and kin, and have a good ol' time.
Different word usages and vocabularies have their time and place; all of them are priceless when used properly. In some ways this is like asking what wine is the best or what tool is best; it depends on what you are trying to do with it. That is a small part of what makes language such a wonderful and vibrant (and delicious) field of endevour. (Is it legal for an engineer to love language?)
When I am writing a spec, I must use the appropriate language (the rules are strict). When I am writing global corporate policy, ditto (strict rules, but the rules differ considerably). When I am trying to sweet talk a US supplier to ensure we have the parts we need when we need them, I usually need to be a fine su'thun gentleman. When trying to sweet talk a European supplier, it's best to use a hint of a Scots-Irish accent. When dealing with Mexicans, I am Chilean (obviously this is not in English, but the same principle applies). It's hard to argue against whatever provides the best communication and gives the best results.
Case in point: Several months ago a white supremacist came into the bar. He was spouting the most vile and ugly hate-ridden rubbish you never wanted to hear. My speaking in deep-deep-south got his attention. The ensuing debate over the US Constitution and the Bill of Rights held his absolute attention. I proved him wrong, by his standards, and told him "Y'all might want to reconsider your position." (and bought him a beer).
"Y'all" was used in the demonstrably singular, but the plural was implicit. He needed to reconsider his position, but his friends also needed to reconsider their positions. Please do correct me if I'm wrong, but I don't think our language has a case for speaking to an individual (singular) and implying a group (plural by the greater meaning?).
Much is left to the artistry and skill of the speaker (or writer), as it should be. No set of rules could possibly encompass this universe of wonders.
He came back a week later to apologize to many people, and to buy me a beer. He is no longer a clan member. He wanted some further advice. Language can be a powerful tool.
- A