When a new plant opens virtually all the laborers will be Chinese. Some of the low-level management may be Taiwanese. Higher level management is Taiwanese.

The Taiwanese low-level management and laborers are there to teach the new laborers and managers how to do it. And over time they leave and are replaced with Chinese.

So in a "mature" factory all the laborers and low-level management will be Chinese. And the upper management will be Taiwanese.

Yes, profits flow to Taiwan. Obviously a lot of the money generated stays in China as it goes into taxes, workers pockets or to suppliers who tend to be local.