Transit in Guangzhou

Yes, of course. Anyway, your itinerary has to have different countries before and after Guangzhou to be eligible. For example, if your itinerary is:

Hanoi - Guangzhou - Seoul

or

Bali - Guangzhou - Bangkok

This is eligible for 24 hour visa free transit and you don't need any kind of visa. Also, it is perfectly allowed to have two separate tickets and to travel on two unrelated airlines. Anyway, you should keep in mind that you will have to approach 24 hour visa free transit counter upon your landing in Guangzhou where you will apply for a temporary entry permit to be allowed to exit the airport because you will have to collect your luggage and to perform a recheck for your onward flight.