We rode the Denali Star from Anchorage to Denali gold star service with breakfast/lunch, and then Denali to Anchorage adventure class.
Everyone loads the train at the same time. They open the door, and everyone walks through.
I recommend sticking with the gold star service. The view is better from higher above (it's the pic with the shaded glass on top, which seems to defeat the purpose), the seats have a tray and a foot rest, and are more comfortable/larger. No carry-on; you need to check all luggage. The food is pretty good and it includes two drinks. They didn't say anything about breakfast until we'd been on the train for 45 min. We had to sit with another couple which was odd but okay.
Adventure class is down below. It's like riding a bus or a plane. There's a rack above for a carry-on. The window is large (it's' the pic without the shaded glass on top). It's kind of noisy. There are families, kids, crying babies, etc. The seats have no food trays or foot rests, and don't lean as far back. The cafe is lack luster, with pretty lousy food choices. You might not be willing to eat any of it. You can bring your own food but you cannot bring alcohol. The cocktail drinks are $14 each and it's not easy to get one in Adventure class because there isn't much service there. There are a few eating tables next to the cafe.
There is a person narrating what you see the entire time but sometimes only the people in gold star service can see an animal or whatever is spotted. We saw moose, swans, caribou, etc. We did not see Denali mountain because of the clouds. The first 2-3 hrs going from Anchorage to Denali is only birch trees, quarries, and run down houses. I suggest bringing a book for that part, but don't worry the views get much better after that. read more