Hi, I'll be leaving Bangkok flying into Shanghai for a 20 hour layover.

Eventually flying back home to usa. Do I need to wait in line to apply for 72 hour transit? Or I can walk freely outside to enjoy Shanghai? What is the process? What do I need? Since my layover is 20 hours yet connecting, do I need to claim my luggage? Thank u. First time having a 20 hour layover I want to take advantage and see Shanghai.