mixed bag vs assemblage

mixed bag and assemblage both are nouns.

Word	Noun	Adjective	Verb	Adverb
mixed bag	Yes	No	No	No
assemblage	Yes	No	No	No

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

Other hypernyms of mixed bag include accumulation, aggregation, collection.

mixed bag (noun)	assemblage (noun)
a collection containing a variety of sorts of things	the social act of assembling
	a system of components assembled together for a particular purpose
	a group of persons together in one place
	several things grouped together or considered as a whole