What is the max safe water temp you should see on a cossie?

I was stop - start on the motorway recently and temp gauge went up to the top of the N of the 'NORM'. It didn't go off the gauge but SECS was showing 98 deg C. I wasn't stopped long enough to see if it would have gone any higher.

Maybe a stupid question but what is the advantage of having an in-car fan switch? I assume that the moment the water temp goes above 89 deg or whatever it triggers at the fans will start anyway and not stop until it drops down again. How will having a manual switch make it better or is it just a case of switching it on earlier than the thermo switch.

Cheers.