Hi
1) you can follow the following article for mysql configuration, from build.properties section.
https://community.jboss.org/wiki/SetUpJBPM54FinalInstallerToUseMySQL-OrHowToRunSection37OfTheUserGuide
after changing the files you will have to fire the following command "ant install.db" instead of "ant start.demo.db".
2) For minimal environment you can deploy the war files available in the lib folder of the jbpm-installer. you can deploy "jbpm-human-task-war-5.4.0.Final-EE6.war" for human task implementation and "jbpm-gwt-console-server-5.4.0.Final-EE6" fro jbpm server engine.
Regards,
Irshad