It's common for teachers not to sign the actual employment contract until they reach China, although of course they should send you the contract and all the other paperwork for your consideration. If as you've said you've read other reviews on this site then you're likely to have seen some posters complaining that the contract they saw prior to arrival was not the same as the one they were presented with when they got to the school, This is a risk and You'll need to use your own judgement on the people you're talking to. The other thing you might have read is when people arrive at a school and are presented with a different contract but then decide to give the school the benefit of the doubt anyway. Don't do this! Leave immediately! You should always have a contingency plan when arriving in china (and any foreign country).

As for the specifics of the contract such as holiday pay, the best thing to do is ask your employers and get written confirmation. The way that the school/recruiter deal with any such questions and concerns will also tell you a lot about them so be sure to grill them on any and all aspects of the position and contract.