I don't know if there were alternate courses of action available that could have better secured Russia's interests at lower cost. But certainly I think that if you are going to make the decision to go to war, you should not half-ass the enterprise as they have done and are still doing. Russia should have at least two million troops in Ukraine right now, rotating from armed forces numbering at least ten million. The only compelling explanation I can think of for Moscow's failure to mobilise resources to match their rhetoric is that the current regime in Moscow does not believe that it would survive the attempt, which is to say that they failed to sell the citizenry on the importance of the enterprise, which is itself suggestive.
Regardless, Russia is achieving China's purpose. They have proven to the world that holdings in USD and USD-denominated assets are readily frozen and stolen, thus kicking off global de-dollarization. Furthermore they are serving as a strategic distraction for the US in particular and the West in general (not unlike the GWOT did). This gives more strategic breathing space to China in Asia. Lastly, their market has been turned over to China, which bolsters China's economic power and ability to fight the West on equal or superior terms.
So long as Russia doesn't lose, it doesn't especially matter for China if they win. If Russia gets into a position where a strategic loss seems likely, China will find a way to intervene indirectly via arms transfers from Iran, North Korea, The Stans, etc. Otherwise, an unending conflict serves China's interests just fine. It also gives China diplomatic leverage to take a leadership role in settling a peace, as they did for Iran and KSA.
