It's rather confusing unless one sort of sticks to one geographical area. I think that's where the definitions are pretty well set. The Redbones have been quantified as 1/4 european and 1/4 black and 1/4 native in something I read on them years ago. Now, I'm not sure what the 'last quarter' has to be. Melungeons are sort of the same mix from what I've read on them. Some of my Helton kin were wondering if we were in that catagory because we cannot trace our roots before 1830. One did a DNA thingy and there was no "African markers" and the Native American marker is not defined by tribe. (darn it).
Then you can toss in a few other classifications, Creole, Cajun, Gypsy. Sometimes it's easier to not over think it. You can get very confused if you do. Whatever the mix, the genes get passed on. We had a "Creole Society" here waaay back and they even had a meeting hall. Now you don't hear about it unless you go looking for it in the archives.