Books Online seems to be quite clear that DATABASE_OBJECT_CHANGE_GROUP applies to any databas, and there is a warning that this can result in large logs.

As for the question of model, I don't know. The audit specifications would surely be copied, but I would not count on that they be active automatically.

In either case, you should absolutely test. And if you audit DATABAS_OBJECT_CHANGE_GROUP, you should particularly check what happens when you create temp tables. Depending on the nature of your applications, this may happen a lot - and you pronbably don't want that to be audited.