If there is the political will, a united stance by western nations will be more than enough to face up to any Russian move on the Ukranian border. Its all down to how many casualties we are willing to sustain. Table top tactics will have already been played by western military hierarchy. The head of the armed forces will inform the politicians that they can win the war........but sustain **% casualties in the process.
It's way more complex than that.
Any invasion of Ukraine causes distraction, and that gets taken advantage of - an escalation on the Poland / Belarus border and excuse for Russian assistance. A Russian ship bumps into a NATO ship in the Med or Black Sea, a Russian/US clash in Syria or Libya, Iranians use this to attack a yank boat in the Gulf, China seizes the opportunity to invade Taiwan.
And then there is no way to predict how things will escalate, or for how long things will stay conventional.
It may even be that any attack on Ukraine may not be the actual objective, but part of a grander plan.
It is a massive game of chess with umpteen possibilities, not just a simple estimates based on a local or confined ruck
Whilst Russia does have genuine fear of NATO presence on it's border (however unfounded) they too weigh up all the scenarios and despite the rhetoric do not want a war with NATO - although they may with Ukraine.
But yes I agree that the political will is needed to deter, and as you will be aware of, there is the non-public capabilities and possibilities that only each others militaries will be aware of and that tends to provide the greater deterrence.