Militarily, the mongols were FAR more advanced. The best analogy is, imo, modern US air supremacy in the middle east. They were simply untouchable until the advent of long range gunpowder. It was their political structure that prevented them from conquering the entire world. Dan Carlin has a good podcast series called Wrath of the Khans that goes into this in depth, in a very entertaining way.
Not really. China had their own nomadic allies. And so did the Qara Khitai. The Mongols also destroyed the Cumans. And many Turkish Empires that were still connected to the steppe and had the same technology as the mongols.
but previously they squabbled bitterly and thus reduced each other to nothing more than nomadic tribes. The “upside” of ceaseless internecine conflict served to sharpen their tactics to a mental ferocity and lethality that hadn’t been encountered anywhere in the more “Pax catholica” European areas or Pax-Jin empires. And as far as weaponry: Steppe warfare / Persian horse archer tactics weren’t new obviously, but the mongols employer recurved bows and multiple mounts exclusively whereas the Jin empire relied more on spear warriors and some archery which was helpless against Mongolian siege tactics and again —- once the walls were breached —- horse archers who could shoot by some estimates further, with more accuracy and with a shorter draw than the British longbow ( another nearly untouchable weapon (when massed) of the same period ). Europeans relied on their heavy cavalry which was basically like Putins tanks today vs Javelin missiles.