top side vs upper side

top side and upper side both are nouns.

Word	Noun	Adjective	Verb	Adverb
top side	Yes	No	No	No
upper side	Yes	No	No	No

As nouns, top side and upper side are synonyms defined as:

Other synonyms of top side include top, upside.

top side (noun)	upper side (noun)
the highest or uppermost side of anything	the highest or uppermost side of anything