Gonna give my take on this. China didn't build 7,000 nukes like the Soviet Union because there's no reason to need to bow up the world 7 times over or some other ridiculous number like that. China's official count is what, 260? And what's the real number? No one knows? I think they should make some 2K, less than 3k and leave it at that. But as it is now, no one wants to go to nuclear war with China unless existentially threatened and that's the nukes getting the job done already.
PLA's conventional forces aren't going to need to match USA+Japan's forces to stop them from intervening in case it needs to invade ROC. This is an assumption that 1. both are willing to fight to the death to defend Taiwan and 2. the geography favors no one, both of which are false assumptions. The geography makes it much easier for China to fight than other countries coming long long ways (China has land-based missiles that can keep carriers away and possibly even destroyer-sized vessels soon) and other countries are going to be far less committed in the fight than China. Even if foreign forces think they can win, they do not want to explain to their citizens how they lost 20,000 sailors/aviators, 50 military vessels trying to defend what turned out to be a smoking rock. The Japanese may, because many there consider China an existential threat, but if the Americans do not go all out, Japan is going to sit on its hands and curse.
So in summary, China's current forces are enough for no one to want to fight to the death for an island that they don't own (in the same sense that no one wants to get stabbed 6 times fighting for a Snickers bar on the ground even if he believes he can ultimately survive and the other guy won't). If not, China would build more nukes, easily (have they?). Currently, they are trying to integrate Taiwan peacefully, but if it doesn't work, even now, I highly highly doubt any country is willing to fight the full power of the Chinese armed forces and possibly eat a few nukes trying to defend an island they don't don't even formally recognize and one that they won't own even if they win.
