Key to classes...
1 = 1st class sleeper. S = 2nd class sleeper (air-con). s = 2nd class sleeper (non-air-con). 2 = 2nd class seats. 3 = 3rd class seats. R = Restaurant car.
DRC = Diesel Railcar express with 2nd class air-conditioned seats, meals included.
Most western travellers use cheap & comfortable 2nd class sleepers, although others are happy to pay more for 1st class 2-berth sleepers.