Russia is showing restraint in Ukraine because they are a bunch of drunk, corrupt losers. They are basically still operating with the old soviet methods. Remember, Putin has grown up with that system and made his career in the KGB. Thats what he knows best, and what he wants to continue. But Russia basically sucks in all aspects. The only thing they have working for them are the natural rescources, like oil, gas, ore and so on.
The Chinese on the other hand are the complete opposite. And China has only one interest, which is China. Its like Churchill said: "In geo-politics there are no friends - only interests." And thats valid for all countries, also for those in NATO.
I wouldn't even rule out that the US (or the western alliance so to speak) strike a deal with the Chinese if Putin keeps annoying them: China gets Siberia, and the west gets the european part of Russia. And there is nothing the Russians can do about it - other than to blow themself up with nukes.