You might use DefaultDS for all. I prefere two different datasources.
If you use JBossMessaging the JMS messages might be stored in the database, HornetQ (the default) does not need a database
Also the EJB timers, juddi ... use the DefaultDS, you might remove the services if you do not need it.
You might also remove the grant, for the first start you might get the table structure from a test DB (if the DBadmin prefere no CREATE grant )
I think there is no documentation for the tables. But if you do not use the former JBossMessaging and ejb timers the tables are not used.