Russia will use nuclear weapons.Russia can take on one country at a time but it cannot challenge NATO as a whole.
Have a look at NATO defensive positions:
More coming:
NATO's Eastern Flank To Be Fortified By U.S. F-35s, AH-64s, Troops
Biden ordered the deployment of additional American forces after declaring that Russia has invaded Ukraine.www.thedrive.com
Russia will loose much of its army in the Baltics, let alone be in the position to advance further. There is too much ground to cover and NATO technologies are incredibly sophisticated on top. NATO is far more capable in network-centric warfare techniques and operations in nighttime conditions.
Even if China provide troops to Russia in Baltics, they won't may any difference.
If the Russian navy is wiped out, the NATO navy will also be wiped out with nuclear weapons.