The seats are larger, sometimes more plush. There is more room for luggage and generally will be less crowded as most Europeans using the train travel in second class. Scotland generally offers only one class. If the bonus is free, it counts as a train day. If it is a discounted bonus, it does not count as a train day.
Discounts are sometimes available as a passholder.
All overnight accommodations require reservations. The Glacier Express runs from St. Moritz to Zermatt. Reservations are required. No, days must be added at the time of purchase. Your pass can be validated by presenting your railpass and passport at a train station ticket window, prior to boarding your first train.