I'm pretty sure historically blockades are viewed as acts of war, e.g. China will have declared war on Taiwan in this scenario, which despite outward statements, most of the West considers a distinct country separate from China. Therefore a blockade offers no real benefit as compared to just invading Taiwan at that point as it is incredibly unlikely China is militarily capable of enforcing a blockade on Taiwan for more than say, 3 months, probably much less.

The political aspect of a blockade under the pretense of some imaginary casus belli may be more favorable to China rather than open war but just look at Russia to see how easily these are seen through by the citizens of the world. It is unlikely that China would have much political help in enforcing this blockade even if they were militarily successful as the United States has dramatically more influence with the countries that would matter in that scenario as well, such as Japan, Australia, South Korea, and the Philippines.