What is the difference between Soft Sleeper and Hard Sleeper? And Deluxe Soft Sleeper?

Hard Sleeper is open and comprises six fixed bunks, arranged as an upper, middle and lower on either side. Soft Sleeper is private compartments which are fitted out to a higher standard. Deluxe Soft Sleeper is the top level sleeper and the most expensive ticket on a train but only equipped by a few of trains. And the following link may help you:
https://www.travelchinaguide.com/china-trains/tickets.htm