If you buy your tickets 14 (?) days ahead, you get almost half price, but that special may not be refundable. Prices go up depending on how many tickets sold.
My Amtrak travels have ranged from long distance to close, on regular Amtrak. It depends on weather, and who is on the train, the conductor, the area you are traveling, factors that can make a good trip or horrible, and my patience for what can go wrong has run out at least temporarily. If you can afford the luxury and private cars on Amtrak, it might be really good? I don't know anything about it. Amtrak is no faster than driving at least in the Northeast. If you want to get there faster, go by plane.
If you are traveling Amtrack's Excela (forgot the name) train, it is the higher priced and takes priority on the tracks. The regular Amtrak has to wait for it.