BA have 'hand baggage only' fares so it will cost you to put bags in the hold.
The fares are optional and displayed alongside standard fares (which are not that much more).
FR allow a standard IATA sized bag plus a personal item in the cabin just like legacies.
Two bags on BA, and I've not had any issues with two bags on AA or UA on US domestics either. Although I don't take the piss on the second bag, so maybe that's why I've not been challenged.
BA A32S cabin may have slightly more legroom
"slightly" ? grab one of those magic emergency exit seats on the new A32's and you've got a whole seat's worth of legroom !