grab bag vs smorgasbord

grab bag and smorgasbord both are nouns.

Word	Noun	Adjective	Verb	Adverb
grab bag	Yes	No	No	No
smorgasbord	Yes	No	No	No

As nouns, smorgasbord is a hypernym of grab bag; that is, smorgasbord is a word with a broader meaning than grab bag:

Other hypernyms of grab bag include assortment, miscellanea, miscellany, mixed bag, mixture, motley, potpourri, salmagundi, variety.

grab bag (noun)	smorgasbord (noun)
a container from which a person draws a wrapped item at random without knowing the contents	an assortment of foods starting with herring or smoked eel or salmon etc with bread and butter; then cheeses and eggs and pickled vegetables and aspics; finally hot foods; served as a buffet meal
an assortment of miscellaneous items	a collection containing a variety of sorts of things