the only writer i would be completely comfortable with labeling as southern gothic is flannery o'connor, i think.
i feel like i am the wrong person to ask. west virginia is actually not in the south, and even if you, like most people, thought that it was-- i'm an outsider myself. (i am making an assumption that you are asking me this because i live in WV, so forgive me if i am wrong.) i grew up in southern california, in a neighborhood where everything is clean and white and the only bad stuff that happens happens behind closed doors. because of this, the whole southern gothic thing is fascinating and appealing to me probably in the same way that it is to you-- it seems "authentic" and mysterious and exotic. it also seems very "american" to me, in a way that coastal california can never be. "salt of the earth"-type stuff.
in southern california, the people who annoy me are people in big expensive german cars who act entitled. in west virginia, the people who annoy me are drug addicts. drug addicts are generally more interesting and mysterious-seeming than rich assholes.
but there is something incredibly inaccurate in this... drug addiction, observed close up, is incredibly boring and pathetic, and not interesting and tragic. poverty isn't more "real" or "authentic" than being upper middle class, it's just more difficult. and a lot of times -- in america, at least -- we treat poverty as though it is some sort of stamp of "authenticity" -- like you grew up poor so therefore you know what you're talking about -- but the reality is that poor people are silenced and looked down on and thrown into jail, etc. people talk about problematic tropes like the Magical Negro; i kind of think the appeal of southern gothic falls into the same sort of thinking... the Magical Poor Southern Person, or something.
but there is something legit in the idea of it, something non-exploitative... something dark and scary and enchanting... the land, when you go to west virginia, feels heavy and full of death. at night i see weird shadows coming out of the mountains. i haven't really been to mississippi, but scott says it is like that and more there. i do think you can feel the history of a land in its soil-- when i visited charleston, south carolina, it was a very beautiful city, very clean, but something in it felt just heavy and dirty and full of pain. in san diego, the only time i ever get anything interesting off the soil is in the wild areas, like the canyons.
i am going to new orleans for the first time at the end of the month and very excited about it-- the thing that appeals to me most about new orleans is its magical/witchy history.
maybe i would have a better answer for this after living in WV for longer.