Travelling by myself.

From bits I've picked up from here and another forum, on a good day, it should take an hour or so from the plane to one of the stations.
Hit an queue and who knows?

Just looking for something cheap and easy to get me from Munich to Salzburg fairly quickly.
20 minutes difference on fast and slow trains is fine although something more modern would be nice for my first rail trip in the area (but getting there is my priority even if I have to stand for an hour and a half).

My experience of booking certain fixed times in the UK is that I generally end up having zero problems en-route and end up hanging around for say 2hrs whilst 3-4 others train depart.
Know fine that if I make connections tight, something will inevitably go wrong.

Some of the airport trains in the UK allow you to get on the next similar service should your incoming flight be delayed (eg Transpennine Express from Manchester Airport allows this).

If I buy a ticket in advance, I've no real idea if there's any flexibility on it.
Some mention semi-flex but don't give details of exactly what this means.
Don't want to pay possibly double for a flexible ticket.