You can get a rough idea of seats on AA by trying to buy a ticket on said flight. Then it will have the seat map.

Depending on how far out it is, some of those seats might show available, but you also have to keep in mind that the Basic Economy ticket holders get seats assigned. Depending on how close it is to the flight, the number of seats showing might be off. Not 100% sure on that though.

They could have already assigned seats, internally, to the BE folks and what you see on the seat map is legit.

Either way you’ll get a fairly decent idea.