OK, thanks for the reassurance .It will depend on the institution. If they send you a contract, then sign it. They may hold the contract until you can prove that you meet all of their hiring criteria -- i.e. graduated med school, passed your exams, have a training license, pass a drug test, etc. Other programs will have you sign a contract, and then nullify it if you fail to jump over one of the hurdles.
The key is not to worry. If you've taken PE and the score comes out in a few weeks, you're totally fine. Even if you were to fail the damn thing, you'd still have time to take it away. The AOA match is just as binding as NRMP.