Highly likely this time it will be serious, full scale war. Baku was preparing for it for years and has superior fire-power, better equipped, more numerous army.
The Armenian PM Nikol Pashinyan cooled relations with Moscow to be close to Washington. So Putin has no reason to help him at least just now.
Russia, Armenia and 4 other countries are members of CSTO.
In 1982 NATO didn't help the UK during the Falkland war for similar reason. I mean direct military help.
But NATO didn't have the likes of the Wagner Group for plausible denialability of military operations in the Falkland War