Yes, I've heard that sitting on the RHS is recommended - but presumably everyone .else knows that too! I assume a 'red cap' is a station assistant.
A "Red Cap" is a station luggage porter. It is a very old term in US railroading. Unfortunately, Albany is not one of the stations where their services are available, which is only offered at a few of the larger stations.
Amtrak offers baggage assistance and temporary bag storage at many stations.
While I have not ridden the Ethan Allen Express, I have ridden the Maple Leaf several times. The train usually has a good load onboard the time it gets to Albany. However, the crew usually has one coach locked off that they open up at Albany. On the Maple Leaf it is the coach furthest forward. Since both trains have Business Class/Cafe car on the rear, if the Ethan Allen Express' crew follow the practice of locking off a car for occupancy at Albany, it'll be the forward most car as well.
Albany controls access to the platforms. You will not be permitted down to the platform until the train is called and there will be an agent checking tickets at the top of the stairs. My experiences on the Maple Leaf and the Lake Shore is they typically will not open the train for boarding by Albany passengers until the engine chamge is complete.
Assuming they have blocked a coach and it is on the head end, my advice is to be towards the front of the boarding line (which will likely start to form before the train is called), and head toward the front of the train once down on the platform, to your left facing away from the station headhouse if going to NYC.