In the first method, the joint case file adopts domestic priority. The first two invention patents will be considered as withdrawn when you submit the joint case file (application date), while the invention authorization at the back will take 2-3 years, so personally, the risk is still a little big.
The second method, directly applying for PCT and re-entering China, is not obvious. Because the content of protection has been reflected in the first two patents, unless the patent behind you is a big and useful improvement on the first two patents, it needs to be added to the claim. And there will be problems for you to consider.
Therefore, if it is only a simple merger of the first two schemes, it is suggested to apply for PCT directly, enjoy the priority of the first two patents, and then not enter China. The protection of China District is guaranteed by the first two inventions, and the protection of foreign countries is guaranteed by the patents authorized by PCT to enter foreign countries.
I wonder if it's the answer you want. (*^__^*)