In Migration guide's 5.12. Migrate Clients to Use the WildFly Configuration File, there are examples of jboss-ejb-client.properties and wildfly-config.xml, these two examples are supposed to be equivalent, but in fact, the legacy jboss-ejb-client.properties specifies the target of the EJB client connection, whereas the wildfly-config.xml doesn't - it only contains security related things.

For an example how to configure the EJB client targets in wildfly-config.xml you can look here https://github.com/jmartisk/mock-artifacts/blob/master/ejbclient/eap7.1-config-secured/client/src/main/resources/META-INF/wildfly-config.xml