The Chinese don't give a damn what you do outside of China (unless it is a universal crime like robbery or murder). But one thing I would suggest you do is that if you go, get new clothes to take with you and new shoes. I live in a place where marijuana use is fairly common, and while that is no big deal, if they find marijuana residue on your clothes they might still arrest you even if you don't use marijuana and are unaware that it was on you.

https://www.reuters.com/article/idUSL26929115/

This is what happened to someone in Dubai who was sentenced to 4 years for 0.003 grams of marijuana on his shoe. China is a country that similarly has a zero-tolerance policy regarding drugs, and Chinese media portrays drug smugglers and users in ways that would make an 80s action movie hero blush. This is probably owing to the cultural trauma they had with the opium wars and opium use (which was primarily introduced to them by the British, but the world then acted like it was an age old problem that they needed kind white folk to help them with. The CCP after the Chinese Civil War adopted such a draconian anti-drug war that drug manufacture disappeared... they would basically massacre entire villages if they found any drugs being produced or grown).