Don't see how Russia succeeding in a winning settlement of an artillery war on its land borders would greatly change China's chances of success using their much bigger army to wholly capture an island which the US might honour its commitment to directly intervene to defend. Russia having a horrible time of it is a reminder to China that military annexation of Taiwan wouldn't be easy, but the basic problems with trying (even a victory would involve absolutely levelling what they consider to be their own territory and kissing goodbye to most of their overseas trade, and the US might actively intervene to defend Taiwan) remain the same regardless of Russia's success or failure, as will their confidence their own army doesn't have Russia's weaknesses.
I suspect the Chinese are more bothered about the delicate balance of other consequences (strength and unity of West, central Asian nations prioritising China over Russia for alliances, Security Council implications, trade implications) and aren't necessarily sure which outcome will be best overall for them.
Russia's success in taking Ukraine, and eventually big parts of the EU, was somewhat hinged on the idea that nato, and to a lesser extent the EU as a whole, could be broken up by doing things like threatening Germany with a cutoff of natural gas.
This sort of breaking up of NATO cohesion would allow China and Russia to act more freely in the world without a unified opposition.
What China and Russia were betting on was that the EU would be weak in the face of tension, and realistically that was a pretty good bet because the EU looked pretty.
They attacked, that didn't turn out to be true, and all their best laid plans are going to shit before their eyes as the EU unifies in the United States pros like 10% of our military capacity at Ukraine and manages to make a tiny country of like 25 million people compete effectively with the country of 150 million that is like three times the size.
China still wants Russia to be a strong unified country, because they want a Russia opposed to the west so that the west is now divided between two fronts.
But aside from that, every single one of their plans has gone about as long as it possibly could have.
Russia was not able to take Ukraine but in a few days
The west did not fall apart
United States has gotten stronger economically.
Economic sanctions have been incredibly effective, without firing a single shot.
It has become clear that given a choice between security and economic progress, countries choose security. China was betting on the ability for their large experts and import market to prevent countries from standing against them.
People were claiming this was going to be the decade of authoritarians against waning democracies, but all of a sudden it looks like this is going to be the decade of strong democracies against waning authoritarians.
It's about the international reaction, not (only) about the outcome of the fighting itself.
China can see the price the intensional community levies upon a war now, and, in case Russia accidentally wins, they can also see the price of occupying an otherwise independent nation.
Mind you: Taiwan isn't recognised as an independent nation by nearly as many nations as Ukraine is.
I suspect the Chinese are more bothered about the delicate balance of other consequences (strength and unity of West, central Asian nations prioritising China over Russia for alliances, Security Council implications, trade implications) and aren't necessarily sure which outcome will be best overall for them.