BMI needs to be under 30. Blood pressure 130/80 and below. Everything else they'll work with you on. No irregular heart beats.
Everyone I've talked to likes Unicaviation if they handle SF, if not they still probably can. Every agency basically can work with any carrier. I will say pick the carrier you want to work at for the long term since changing carriers barely exists since you have to have your medical released by your current carrier to move to another and they hate doing that. Even when contract is up.
Start the proccess now. Everything takes forever in China. Tons of paperwork and many visits for medical, sim, ATP test. Start studying for ATP test now. Plan on 6 months before you get on line and that may be quick.
Good Luck.