What about land usage? In ancient china(and china now) there's not much land to farm, so they developed advanced techniques to fully utilize the land they had available to them.
But somewhere like Egypt, they just threw seeds around and let their oxen trample them. The only irrigation they particapated in was building large square pits that filled with water.
The Chinese had to work harder, and develop better ways of making food, because they live in a mountainous land. While the Egyptians didn't have to do that because they lived next to a river which flooded regularly, and was really good for agriculture.
Will land affect that kind of stuff? Will isolated people develop less weapons/be less warlike?(More likely the former)
Hm, sorry to burst your bubble, but you're thinking about
Japan and not
China in the example you gave. Japan is mostly mountainous terrain with poor fertility, and most of the country's forests annot be chopped down because it would anger the Shinto Kamis. So Japanese people had to develop things like terrace farming and be an overall efficient and well contained people, their whole culture revolves around that; it's also a reason why the world's biggest fish market's on Japan, figures an island by the sea might be a poor cropland, but it's really good place for fishing.
China, though, was the world's biggest country for ages,
most of it is plains, several of those plains have rivers flowing through them that make irrigation possible. That's why China always had such a stupidly huge populace. They actually have so many people that they need a lot of food to feed them all, and thus their large population is both caused by their huge farmlands, and causes it. They developed several ways to increase the productivity of the soil just so they could feed that massive amount of people. You can say that much of China's territorry is not usable for farming, but China's territory is huge. I'm not saying that they didn't terrace lands or things like that, by the way.
By the way, I'm talking about de facto China here, not Tibet, Uyghuristan and the parts of Mongolia they conquered.