highly strung vs high-strung

highly strung and high-strung both are adjectives.

Word	Noun	Adjective	Verb	Adverb
highly strung	No	Yes	No	No
high-strung	No	Yes	No	No

As adjectives, highly strung and high-strung are synonyms defined as:

Other synonyms of highly strung include edgy, jittery, jumpy, nervy, overstrung, restive, uptight.

highly strung (adjective)	high-strung (adjective)
being in a tense state	being in a tense state