Now, is this an expression in Italian, like it is in English, where it means "pretty much"?
According to Wiktionary, yep https://en.wiktionary.org/wiki/pi%C3%B9_o_meno#Italian
Couldn't this also be translated as "plus or minus"? This is also a common English phrase.
Interesting. I'm American, and I've never heard of that phrase before. Learn something everyday.
Can it be used like Spanish "mas o menos," like when someone asks "Que tal?" and you answer "mas o menos" (like English "so-so" / "not bad")
Also "more or less" is a translation of "más o menos". I should know, im a native spanish speaker, (I'm from Puerto Rico)