Knowing when to get on/off the train is as simple as knowing the train schedules. Know what time you are due to arrive at your destination and plan to be at or near the door at least five minutes ahead of time. If you are blocking the exit you'll find a lot of people willing to help you with your luggage (after all, you are blocking their way!)
1cl versus 2cl. The former, being more expensive, translates to fewer people. Will you always be able to keep your luggage with you? Maybe not - but keep it in plain sight and within quick reach.
The referenced document (mine) talks about luggage. Give some real serious thought about what you are packing and why. I just got off a 7 NT Carib. cruise and I took one 24" bag (plus backpack for camera stuff, etc.) I had stuff I didn't wear! I got my wife down to a 21" and a 24" and she had a bunch of stuff that she didn't wear. If you are going to cruise AND travel by train then you need to cut down on the luggage.
If someone were to offer to help with the luggage for x euros or dollars, I'd send them packing. They probably have a friend a suitcase toss away that is working with them.