Seven minutes should be enough time. Just be aware of the arrive time for your change and grab your bags and be prepared to disembark by moving to the exit.

Note that if you should miss your connection, service runs every hour from Saarbrucken Hbf to Koblenz, so you won't have more than one hour to wait.

The DB timetable takes the layout of each station into account when suggesting connection. As long as you're not handicapped it should be no problem to make it.

Frequent travelers will have a different view on this. For them 7 minutes maybe already 3 minutes wasted waiting time.

If the ICE from Paris is not delayed you won´t have too many problems. In the worst case you would have to wait an hour for the next train, but there are cafes, shops etc. in the Saarbrücken station to spend the time.

Thank you all experts for your comment. Very helpful.