I would expect the war within 2023. China's economy is in deep trouble and the social unrest is growing. A war with India will certainly help diverting the attention without attracting any international sanction.
My date is Sept/Oct 2024 for either a war in the mountains or Taiwan. Both the US and India will be in election mode, making them weaker than usual.
In America's case, both Presidential options are average, so it doesn't matter who comes to power during wartime. In India's case, a loss in the mountains could increase the chances of Modi's defeat in elections, which is of tremendous benefit to both Pak and China.
The Sep/Oct weather is also suitable in both areas.
If Xi wants to grab Taiwan, he can't wait till 2030. By 2030, the world would have significantly reduced their dependencies on China and Xi will not have much bargaining power. He has to act fast so that the world is forced to turn a blind eye and some middle ground will be reached (like Hong Kong model).
Although the world will be less dependent on China, it will still remain dependent. It won't go away in just 7 years. But China will become less dependent on exports by then too, so it works both ways.
My perspective is more on the military side of things rather than economic. The US doesn't have the air assets necessary to fight China today and won't be getting them until 2030, or even 2035.
With that said, I still think the best time for China to invade Taiwan is 2024-27. And China will be at its strongest vis-a-vis the US in 2026-27. Everything that the US considers is necessary to fight China will only start coming in after 2026-27, the F-22 MLU, F-35 B4, AB class Flight III in numbers, Virginia B5 etc. So the Chinese will have a significant tech advantage in some areas until then.
Now, all they need is the opportunity to test their new weapons before risking a war with the US. It doesn't have to be India either, although India is the best option for them.
I don't think the combat experience at Himalayas will help much in Taiwan.
It most defintiely will. It has less to do with terrain and more to do with fighting experience. They need to get into actual firefights, artillery and tank duels etc. Just 'cause there are tactical differences doesn't mean the lessons learned cannot be applied elsewhere. It's not just the army, the air force, rocket forces and navy will gain experience too.
They also need to test their new weapons.