sexual congress vs sex activity

sexual congress and sex activity both are nouns.

Word	Noun	Adjective	Verb	Adverb
sexual congress	Yes	No	No	No
sex activity	Yes	No	No	No

As nouns, sex activity is a hypernym of sexual congress; that is, sex activity is a word with a broader meaning than sexual congress:

sexual congress: sexual activity between individuals, especially the insertion of a man's penis into a woman's vagina until orgasm and ejaculation occur
sex activity: activities associated with sexual intercourse

Other hypernyms of sexual congress include sex, sexual activity, sexual practice.

sexual congress (noun)	sex activity (noun)
sexual activity between individuals, especially the insertion of a man's penis into a woman's vagina until orgasm and ejaculation occur	activities associated with sexual intercourse