回複：Your understanding is mostly right.

In situation 1 b and situation 2. The spouse's country of birth can not help the principal (If I remember correctly from yesterday or 2 days ago, the original poster's spouse was born in Taiwan) The principal will still subject to China per country limit.

In situation 1 a, because you and spouse will be adjust together under the same category, your visa number (as well as spouse's) will both charge to Taiwan, which the EB2 visa number is currently available.