fluency vs expressive style

fluency and expressive style both are nouns.

Word	Noun	Adjective	Verb	Adverb
fluency	Yes	No	No	No
expressive style	Yes	No	No	No

As nouns, expressive style is a hypernym of fluency; that is, expressive style is a word with a broader meaning than fluency:

fluency: powerful and effective language
expressive style: a way of expressing something (in language or art or music etc.) that is characteristic of a particular person or group of people or period

Other hypernyms of fluency include style.

fluency (noun)	expressive style (noun)
the quality of being facile in speech and writing	a way of expressing something (in language or art or music etc.) that is characteristic of a particular person or group of people or period
skillfulness in speaking or writing
powerful and effective language