Wyoming speaks the truth, both good and bad.
Tattoos? I am not sure if this is a problem. But guess what? In China it might be up to the individuals' opinion that is giving you your exam that day. And he probably has little or no training. Maybe he will flip a coin?
Scars? You may need a doctors note on any big scars, especially if it looks like it was sewed up. It will be cheaper for you to get a note before you come, than have to fly back home to get one. They want to know what was done/fixed/broken.
From February to August this year, out of 14 expats at my airline, one lost his job due to a BS medical test, 3 have lost an average of 2 months pay, plus paying for additional medical tests/procedures, attempting to comply with CAAC medical, and one is still out of work due to a minor "infraction".
All in 6 months.
i got lucky, finished my contract, and left. It was a great job. Best flying and schedules I will ever get probably. The company went out of their way to treat us well. But at the end of the day I felt like I was dodging the CAAC frag pattern. They were alway heaving a different grenade every couple of months. I made it out alive and well.