They also do have custom playbooks-- I edited a teams playbook by a few plays and saved it and it appears you can use that online too. I don't believe you can set your own audibles though.
I set my custom playbook as my "favorite playbook" under game options. Then I went to settings and custom audibles and you get a box saying:
--- "Custom playbook audibles cannot be modified. If you wish to continue your default playbook will be changed to the playbook of your favorite team. This cannot be reset!"