As I understand it on AA rewards --
1. If you have a web fare reward - you can not change it - data/time/routing/etc. You must redeposit and rebook based on the current mileages.
2. If you have a non-web fare reward - you can make changes within the parameters.

Of AA rewards - I find it is best to book two one-ways - then you can change one without impacting the other. And for now there are no change or cancellation fees.

Please correct me if my thinking is off.