WI Nationalists Win Chinese Civil War

The US and South Korea would very likely win the Korean War TTL. Vietnam War may go differently too. What would China be like now without communism? A propserous, US-ally democracy China? Or not?

Do the Nationalists rule over all of China or is a PRC-in-Manchuria okay?

I doubt there'd even be a Korea or Vietnam War in this timeline. A Western-backed China would force the Soviet Union to focus more on its Eastern defenses, and the situation in Europe would become more tense. I can easily see the Soviet Union funding rebels in Tibet and Uyghurstan.

Not necessarily; the Tajik republic borders Tibet. They could also smuggle in weapons et al. through Uyghurstan.

I think the methods, let alone the outcome of a KMT controlled China would depend on the circumstances. Chiang's regime is normally seen as massive corrupt and riven by infighting while he sought to avoid anyone else, especially generals gaining any influence or popularity that might mean they could become a rival. If you can get past that then the KMT's chances are much greater. Possibly then something removing Chiang, especially if it causes disfavour for the Communists.

There might be butterflies during the war, for instance Britain managing to hold onto Burma. This would make supply of the Nationalists far easier than having to fly stuff over the hump. Have the KMT better armed and equipped and able to avoid the defeats in 43-44 and their morale and economic position is markedly stronger.

Stalin also supported the KMT, probably more than the communists who he thought too weak. This changed later and the latter gained hugely by supplies and equipment from the Soviets in the Civil War post 1945. However if the Soviets still size Manchuria from Japanese control but the KMT are in a much better position Stalin could seek to mantain Manchuria and possibly some neighbouring provinces as a buffer state under his domination. Which would definitely alienate the KMT. In this case the Korean war is unlikely to occur and if it does will probably be a western victory.

The other alternative is that Stalin feels the need to support Mao for reasons of prestige and to stop China becoming a pro-western state and the conflict in China becomes a much larger 'Korean' type situation. which could seriously affect both western-Soviet relations and the recovery of much of China.

Without this and with the KMT holding most/all of China it could be anything from an economic giant like present day China or a strif torn mess in which a brutal 'nationalist' regime is facing serious internal unrest supported by communists. Something like a Burma on mega-steroids!

  That's been a common condition for much of Chinese history, far more than most people realise.  However given the strength of the Chinese identity and also of nationalism in general I think your only likely to see states separated by very strong idealogical differences, such as between capitalism and communism.