As far as I'm aware, this Russia as a junior partner of the de facto Sino-Russo alliance talking point popped up at the beginning of last year, presumably a half-baked attempt by the Biden administration to drive a wedge between China and Russia.
While China dwarfs Russia economically and outshines Russia developmentally in virtually every aspect, Russia still retains significant advantages over China in several areas including nuclear arsenal, strategic bombers, SSBNs, sphere of influence and political clout in middle east, Africa and Latin America. Russia is not as weak as people perceived to be and (Putin's)Russia will bow to no one. China is well aware of that.
China and Russia complement each other in this anti-Anglo-global-hegemony alliance. Russia can pick up where the Soviets left off, while China provides the economical engine the Soviets never had. Plus, the new Euroasia silk road is far more likely to succeed with Russia's blessing and cooperation. In this alliance, China and Russia are partners on equal terms. And based on the recent developments, this is exactly what the two have in mind.
Exactly the point. Whether or not one country is the largest in the world by size, or the largest in the world by population, both have now become indispensable partners and the very last bastion to resist American perpetual hegemony (since India has practically caved to all American demands).
China and Russia also have the advantage of geography. The combined size of this new polity can project rapid land power across the entirety of the world continent, where 80% of the world lives and 70% of its global GDP. Let America be pushed back to its dominions in the America's, who will also eventually shake of the Washington yoke.