If Chiang wins the civil war, we can assume that he's going to be top dog. Without any external enemies, he is going to sideline the warlords. He will not tolerate them once he no longer depends on them in any way.
Politically, this means KMT China is an authoritarian dictatorship lead by Chiang, either directly or behind the scenes. Some very trusted subordinates may get the actual positions to preserve the illusion of democracy. Like Taiwan IOTL, he will make sure his son inherits power after he dies. There are likely to be rival factions within the KMT (like Li Zongren) which will disrupt this. If so, these power struggles will be the closest thing to a change in government, but true opposition political parties likely won't exist until later.
Economically, Chiang will pursue a policy of a mixed economy. He will implement agrarian reform, but this is something that will be harder to do in China (where many landlords are still politically powerful) than in Taiwan (which was not ruled by China previously, and whose land Chiang could simply extort). However, there will be some available land that gets distributed. Instead of a sudden reform, we probably see this stretched out over decades. The KMT will run some state owned enterprises, especially in heavy industries with military applications. But most of the other economy will be in private hands.
KMT China will avoid the disasters of the Great Leap Forward and Cultural Revolution. The economy will be much better than under the CPC, but probably not as good as Taiwan. There will be more entrenched poverty, but with the greater resources in China, there may be more dynamic companies. I think the key to economic development here will be the example of Hong Kong. Hong Kong companies will continue to invest and develop southern China, and will serve as a check if KMT becomes too statist. US companies will likewise be doing business in China. And the overseas Chinese in southeast Asia and in the US will continue to build ties and serve as financial and educational resources.
KMT China will not be friendly with the Soviet Union, but won't antagonize them either. KMT China still claims Mongolia which will cause issues. Chiang will encourage the end of the European colonial empires. He may become the leader of a non-aligned movement, but ITL, it may be more pro-American. Chinese relations with America will be strong. With the Japanese economy not stimulated by the Korean War, China will likely be the most important Asian trading partner to the US. With the potential of a friendly China ont he USSR's east flank, the US will be less likely to intervene in Asia. They might rely on China to watch over things in Vietnam, or even if Vietnam goes Communist, might not be worried given KMT China is on its doorstep. Tibet may remain independent. I don't see Chiang actually sending troops to invade. Tibet might become a protectorate where China controls its foreign policy, but local matters are decided internally. In fact, all international relations in the 1950s and 1960s becomes very different with a KMT China. None of the European powers will feel comfortable with it, and now they are dealing with China and the US being friends.