small beer vs fluff

small beer and fluff both are nouns.

Word	Noun	Adjective	Verb	Adverb
small beer	Yes	No	No	No
fluff	Yes	No	Yes	No

As nouns, fluff is a hyponym of small beer; that is, fluff is a word with a more specific, narrower meaning than small beer:

Other hyponyms of small beer include bagatelle, frippery, frivolity.

small beer (noun)	fluff (noun)
something of small importance	a blunder (especially an actor's forgetting the lines)
	something of little value or significance
	any light downy material

small beer (verb)	fluff (verb)
	ruffle (one's hair) by combing the ends towards the scalp, for a full effect
	erect or fluff up
	make a mess of, destroy or ruin