Re : want to have a module display only acticles of topic "x"
you have the param topicId=your_topicID you can add in the admin modules panel on the line params
This morning I added in 1.9 CVS a param topic=your_topic_name (topic=public) because the topicId is not a all friendly (I didn't find a way to know the value except to go in the database)
sylvie