Yes, much of my family is from the area, so I have heard of Melungeons, but most of what you read about them is pure nonselnse. Darned few "real" Melungeons will admit to the descent, and those few who do really have no clue what their descent really is. Anyone who claims to have the answers is wrong, and probably 90% of what's written about them is complete fantasy, written without any basis in fact.
Many are swarthy, but no more so than a great deal of non-Melungeons all through the Appalachians. Many are blond and beautiful, and many are dark-haired and ugly.
Odds are even better than fifty-fifty that there really is no such thing as Melungeons, and that it all started because of simple racial prejudice back in the 1800s. Anyone with Native American blood, Jewish blood, or even Irish blood, was often the subject of persecution and isolation, and just like people have always done, groups of like formed.
When these groups happened to be poor, they often became outcasts, the subject or discrimination and ridicule, so they tended to isolate themselves even more, and close marriages produced offspring that perpetuated family characteristics.
All of which means nothing. You can find a different group of something every twelve feet throughout the Appalachians, but in reality, the only real differnces are usually in the minds of "researchers."
By all real accounts I've seen, Melungeons are simply people who have no more unusual characteristics in any way than any other group of people. They simply have the distinction of being singled out by well-meaning, but generally incompetent, researchers.