nom de plume vs nom de guerre

nom de plume and nom de guerre both are nouns.

Word	Noun	Adjective	Verb	Adverb
nom de plume	Yes	No	No	No
nom de guerre	Yes	No	No	No

As nouns, nom de guerre is a hypernym of nom de plume; that is, nom de guerre is a word with a broader meaning than nom de plume:

nom de plume: an author's pseudonym
nom de guerre: a fictitious name used when the person performs a particular social role

Other hypernyms of nom de plume include anonym, pseudonym.

nom de plume (noun)	nom de guerre (noun)
an author's pseudonym	a fictitious name used when the person performs a particular social role