To enable IIOP you must have the JacORB subsystem installed, and the <iiop/> element present in the ejb3 subsystem configuration. The standalone-full.xml configuration that comes with the distribution has both of these enabled.
The <iiop/> element takes two attributes that control the default behaviour of the server, for full details see EJB3 subsystem configuration guide.
To enable JTS simply add a <jts/> element to the transactions subsystem configuration.
It is also necessary to enable the JacORB transactions interceptor as shown below.
Downloading stubs directly from the server is no longer supported. If you do not wish to pre-generate your stub classes JDK Dynamic stubs can be used instead. The enable JDK dynamic stubs simply set the com.sun.CORBA.ORBUseDynamicStub system property to true.