Flying Into & Out of GZ

I just wanted to double check my eligibility for the 72 hour visa-free transit. I am currently living and working in China with a Z type. Upon completion of my job, I will be leaving to travel southeast Asia. During my travels, my Z type will expire. I want to return to GZ just for a day or two to pick up my things on my way back to the U.S. I will be flying into and out of the Baiyun airport. Should I have any problems doing this? I have not yet purchased my tickets into and out of but I know that the arrival and departure will need to be within 72 hours of one another. What about connections? If I am flying from GZ back to the U.S. am I allowed a layover within China or do I need to make sure that my departing flight does not connect within PRC? Thanks!