I haven't heard the Norway link before.Thats interesting and I'd like to see information that supports that.
According to the English Text "History of Kent County" Ralph Bufkin and his descendents lived in that County of England.Thats is the most Southeasterly county near Dover.History of Surnames most commonly indicate that the prefix "Buf" is of Flemish decent.Which is somewhere in the proximity of Amsterdam or Northern Belgium.This makes historical sense since.I would likely suspect the Bufkin name coming across with William the Conquerer, but there is nothing that supports this except the two previous hints.
A norwegian link would have to be viking related.and since Maidstone is inland by a considerable amount, and that most viking towns were on the eastern coast.I find this less likely, (but possible).
The next major source to look at is the Quaker records in Virginia.It amazingly picks up where the "History of Kent county" leaves off.With Leaven and Ralph in Virginia.History of Kent County clearly states that those two brothers were in the West Indies(carribean).This has led to some Theorizing that they were involved in less then honorable trade practices against the Spanish.Which was extremely commmon in the early 1700s.
I think that the 3 brothers to MIssissippi move is a small fraction of the occurance in the US during the 1820s.During that time there is clearly some Bufkin families flourishing in Ohio and continuing as Quakers.This could be the third brother you mention, but I haven't found a link that proves this.But there are many individuals form the SC, NC area who still go by the "original" spelling of Buffkin.(Although History of Kent shows only one F).