IMO, there are 3 distinct differences.
Amongst White Americans you've got the:
Rednecks
White Trash
Good ol' boys
You've also got the yuppies, etc. but we're not talking about them.
IMO, a:
Redneck: A guy who probably wears tight jeans and a tight baseball hat with fishing hook hooked to the bill. These guys are usually very very skinny and wiry. Usually got oil on some part of their jeans. This fellow likely chews tobacco and owns a Confederate flag. He likes to fight even though he's 5'7" 130. VERY CLOSE-CROPPED HAIR. Can usually fix mechanical stuff. Pretty hard-working and serious, but loves to have fun. Loves to hunt and fish. Loves the good Lord. Loves America. If they can't install your 12" subs, can find someone who can.
White Trash: Slightly different from the American Redneck. Less helpful. Not as smart. Wears loose-fitting clothes (think sweatpants and Cowboys jersyes) to grocery store. Shops at K-Mart, Wal-Mart (on payday), Target, Bargain Barn. Eats at Golden Corral, Cracker Barrel, Truck Stops, etc. Has several kids and usually has bleached hair. May or may not be using Methamphetamines. Doesn't really love hunting or fishing. Can't afford equipment. Buys lottery tickets. Likely lives in trailor. Family Tree may or may not split. Doesn't care for America. Thinks the government is keeping them from realizing their potential. Whines a lot. Can't really help you with your car, or installing a stereo.
Good ol' Boy: Likely the most financially-secure of the three. Good ol' boys can be college-educated and likely hold better jobs than Rednecks or White Trash. Loves to hunt and fish. Loves trucks. Loves America. Loves family. Loves the Lord. Likes goatees. Hair usually pretty well-kempt. Active in the community (little league, pop warner football..) They don't usually sport dirty clothing, but they like to wear expensive cowboy boots occasionally. Might own a nice Harley. Loves football, especially at the College level.
I hope this clarifies some things.