Very thought provoking take. But I think Russia will splinter long before China. Specifically the eastern and some of the central asian parts of Russia have no upside to staying in the federation. They are being sucked dry and if Moscow loses its grip from the attrition of a war, things will crack.
I don't have much knowledge of China, it just appears from the outside to me that the State is in much more control.
Russia is way more advanced and united than China. Don't look at GDP figures, these are inflated and a bad measure of how advanced an economy is.
Look at this last coronavirus crisis: Russia was able to procure a more advanced vaccine than China. You'd think the second most powerful and planned economy in the world should have done better but it didn't.
Edit: Another measure to look at it. Look how many countries of the world were affected by this last war with Russia. (either for food, rockets, raw materials, etc...)
I don't have much knowledge of China, it just appears from the outside to me that the State is in much more control.