When you install the JEE server, it will install an author instance into the same JEE environment (IE: it will install an author Jar into JBoss). This author instance should be your primary way of editing Adaptive Forms and generally authoring. For the publish instance, ideally it should be on a separate machine. I definitely would not put it inside the same JBoss deployment. Definitely on a separate piece of hardware. However, what do you need it for? If you are doing AEM Workspace forms and don't need a separate portal, you won't need it.
For the turnkey - yes, plenty of customers deploy turnkey for production use. However, most do opt for partial turnkey and put their data on separate DB's than MySQL though.