excess vs overplus

excess and overplus both are nouns.

Word	Noun	Adjective	Verb	Adverb
excess	Yes	Yes	No	No
overplus	Yes	No	No	No

As nouns, overplus is a hyponym of excess; that is, overplus is a word with a more specific, narrower meaning than excess:

excess: immoderation as a consequence of going beyond sufficient or permitted limits
overplus: extreme excess

excess (noun)	overplus (noun)
excessive indulgence	extreme excess
immoderation as a consequence of going beyond sufficient or permitted limits
a quantity much larger than is needed
the state of being more than full

excess (adjective)	overplus (adjective)
more than is needed, desired, or required