Can I still use my current DS2019 form after I waive my J1 2 years home country service?
-For what?
Or say, should I right away apply for H1 or F1 visa to maintain my status in US?
-Yes. After you get the J1 waiver, you can not extend your J1 any more.
Am I able to go back to China during my pending waive period using my J1 visa?
-If you use a J1 visa to reenter US, your original J1 waiver is invalid and you need to do it all over agian.