or so vs about

or so is not an adjective while about is an adjective.

Word	Noun	Adjective	Verb	Adverb
or so	No	No	No	Yes
about	No	Yes	No	Yes

As adverbs, or so and about are synonyms defined as:

Other synonyms of or so include approximately, around, close to, just about, more or less, roughly, some.

or so (adjective)	about (adjective)
	on the move

or so (adverb)	about (adverb)
(of quantities) imprecise but fairly close to correct	(of quantities) imprecise but fairly close to correct
	in the area or vicinity
	in or to a reversed position or direction
	in rotation or succession
	used of movement to or among many different places or in no particular direction
	(of actions or states) slightly short of or not quite accomplished; all but
	all around or on all sides