What usually happens is they ask for volunteers, though even if you do that they may not need the seat if the oversell situation resolves itself with no shows or rebooks.

If they are in an oversell situation, they may offer AA flight credit vouchers. The value of these could start at one value and increase if people don't accept them. Reasonable? That depends how badly they need the seats. I've heard $800 offers on 1000 mile domestic trips when they needed the seats.

If the next available flight they can confirm you on (on the spot) is the next day, then yes they would usually offer hotel and meal vouchers. Seating, whether on another carrier or not, is not guaranteed to be similar. You could wind up in a middle seat in the rear by the lav.

If you accept the overbook and it's on another airilne, you must get a record locator number for the other airline and confirm right there on the spot (call other airline, look up booking on their web site, etc.) and verify your seat assignment. DO NOT leave the desk or agent until you are 100% sure you're confirmed. There are stories of being rebooked to other airline and then showing up at their counter and being told the original airline didn't correctly ticket it.