(Speaking of AA.)

Nope. As long as you're talking about 1) when towards the end of boarding there's no more overhead space or 2) you're on a tiny plane and nothing fits up there.

I've been researching this a little bit recently, the key dimension is the "height" dimension. If that is under or around 9" then it'll fit comfortably on most flights, and most of the "templates" or "checkers."

Mine and I think a lot of other ppl's pet peeves are when a luggage doesn't fit wheels first. I think as long as it fits wheel first, it should be okay. For many years I was boarding like zone 5 so I'm extra conscious that my luggage doesn't take up more overhead space than is necessary, so that the late boarding folks can still have a spot.