Rednecks - drive trucks, Go mudding, drink lots of beer, proudly live a rural lifestyle. Recreational drugs may or may not be a part of it. They often have a typical job in an office or store. A few are real farmers. It’s a cultural thing.
I very rarely use hillbilly.
Hillbilly - are people who were born into a unique lifestyle. Often extremely poor. Limited education. I’ve known a few families and they were very hard working people. Others I wouldn’t want to get near. Drugs, particularly meth is a problem because of the poverty.
Trailer trash is the most pejorative term around here. I don’t use it. Often it’s chronically unemployed people that sell drugs or commit minor crimes to live. They are often found living in run down trailer parks.
With the western states I think cowboy/rancher comes to mind more than redneck, not that there aren’t rednecks out there, too, since they exist everywhere. The two might have some things in common but for one group it’s because it’s a part of their way of life, whereas the redneck is looking to portray an image. For example, a rancher drives a pickup and uses ATVs because they are most suitable to access their land. A redneck has a jacked up coal-roller just because. Cowboy hat vs baseball cap. Rednecks might like the outdoors, hunt, and fish but could care less about conservation, unlike a real outdoors man.
I hadn’t heard of “hoopie” until this thread, but I’d otherwise agree with your characterization except that redneck is slightly more pejorative than hillbilly to me, since “redneck” to me implies an active anti-intellectualism – someone who doesn’t cotton to the book larnin even if they have the opportunity – whereas “hillbilly” does imply more ignorance of the world than average but doesn’t make a judgement about whether they are eager to cure this or not.