I think this understates what a "China with North Korea-like priorities" can do. It will actually build thousands of ICBMs, trying to get into a similar league as the US and USSR. It will build a surface fleet and a large undersea fleet sooner in its history along with large ground forces. Among its vast Army, it will set aside a certain proportion to make a very large special ops force that will be doing infiltrations and terrorism against Taiwan and the ROC presence abroad. It's military tech will be poor, not benefitting from western and Russian advances in arms technology between 60s through 90s (except some through espionage and illicit trade through Pakistan and others), but it will be very large, with a much greater quantity of firepower (and manpower) than the OTL Chinese military of 1971-2011, along with being a weirder, more culty country. And for all its flaws, it will have nukes that work, in large quantity, and with intercontinental launch capability. The reforming China of OTL, which sought greater international connections, made peace with the fact that it was not in the same militarily league as the US and USSR. This isolated China may not, and the results will be terrifying.