Very little to none. The PRC, economically speaking, doesn’t need Taiwan. Plus the regulations you stated forbidding them to invest in TW.

Taiwanese invested in the mainland because it was easy and what they know. Mostly it’s manufacturing and mostly it’s a legacy form the 90s/early 00s. It’s not done as much now, at least at the same scale.

The culture and the language + traditions bind the two countries so naturally investments follow. But they are much less than they used to be.

Japan has become a bigger partner for investment for Taiwan as has Southeast Asia, mostly Malaysia.