poor white trash vs poor person

poor white trash and poor person both are nouns.

Word	Noun	Adjective	Verb	Adverb
poor white trash	Yes	No	No	No
poor person	Yes	No	No	No

As nouns, poor person is a hypernym of poor white trash; that is, poor person is a word with a broader meaning than poor white trash:

poor white trash: (slang) an offensive term for White people who are impoverished
poor person: a person with few or no possessions

Other hypernyms of poor white trash include Caucasian, White, White person, have-not.

poor white trash (noun)	poor person (noun)
(slang) an offensive term for White people who are impoverished	a person with few or no possessions