How Do You Play Trainz?

[britjay]

I'm new to Trainz. I'm currently playing through the routes included with TR2019.

ECML Edinburgh to Dundee only has three sessions.
ECML Kings Cross to Edinburgh, a £18 DLC, only has three sessions.
Liskeard to Looel, in TR2022, only has three sessions.

All appear to be large, beautiful, highly detailed routes but without a chance to explore them.

I can't find any sessions on DLS, although it doesn't appear to be the easiest to navigate, maybe I've missed them?
Are most players creating their own sessions from scratch? Replaying the included sessions with different locos/trains?
The scoring system is very basic and doesn't give much incentive to play again for better timed runs.

Thanks in advanced