J1 student is good for you since you intend to go back to China. There is no waiver issue until the J1 is finished. Otherwise, it is same as F1.
Also, I don't think you need to go outside of country to change it. I changed from J2 to J1 student longtime ago, you just need to approval of DS539. However, things could be differnt now, better ask people at your school's international office.
Hope this helps