elite group vs upper class

elite group and upper class both are nouns.

Word	Noun	Adjective	Verb	Adverb
elite group	Yes	No	No	No
upper class	Yes	No	No	No

As nouns, upper class is a hypernym of elite group; that is, upper class is a word with a broader meaning than elite group:

elite group: a group or class of persons enjoying superior intellectual or social or economic status
upper class: the class occupying the highest position in the social hierarchy

Other hypernyms of elite group include upper crust.

elite group (noun)	upper class (noun)
a group or class of persons enjoying superior intellectual or social or economic status	the class occupying the highest position in the social hierarchy