Congregationalist vs Protestant

Congregationalist and Protestant both are nouns.

Word	Noun	Adjective	Verb	Adverb
Congregationalist	Yes	Yes	No	No
Protestant	Yes	Yes	No	No

As nouns, Protestant is a hypernym of Congregationalist; that is, Protestant is a word with a broader meaning than Congregationalist:

Congregationalist (noun)	Protestant (noun)
a member of the Congregational Church	the Protestant churches and denominations collectively
	an adherent of Protestantism

Congregationalist (adjective)	Protestant (adjective)
of or pertaining to or characteristic of a Congregational church	of or relating to Protestants or Protestantism