Those are goods plans, but really, just come to Taiwan and live here first for year or two(or five), and then decide about citizenship. Taiwan is truly great in many ways, but it may still be a tough experience to deal with local culture in long term.
Taiwan has a problem with stagnation, in general, local people start with about 30000 NTD (that’s a good start) and finish at about 60000 NTD or so, and it’d difficult to go higher. And 30 years ago it was the same. Promotions for foreigners are hard to get (don’t forget about culture), so it’s really possible to stuck in a dead end.
For places like Science city, where IT guys work, salaries are better. Problem is, like with Korea, if you’re a foreigner and you qualify to work in Science City as a techie, you probably can go to a better place abroad and get twice or triple as much money with much less work stress. Key point of Taiwan is that country is cheap, and you may even get a much better life with 2000 USD salary here than with, say, 4000 USD in Singapore (hypothetically). And it still is a good place to work a year or two to get an experience.
For Mainland, of course they will value Zhejiang better than any University of Taiwan. They don’t value Taiwanese universities that much.
Last, Chinese language is individual. Some people have natural talent for it, some can’t learn it no matter what. For me, for example, tones are a true nightmare, even after 4 years. If you’ll love the culture of Taiwan, you’ll learn the language, if not - it will be an useless struggle.
Again, be warned about Taiwanese PhD programs, things may go really weird. PhD and Confucian values don’t mix well for engineering (Taiwanese students and professors are in the lab 24/7, constantly showing cult-like devotion to their research and teams). But hope you’ll like your stay here, if you’ll come.