A primary strategic objective would to re-establish a geo-political land-link between Kaliningrad and the greater sphere of Russian influence, including Belarus. This would put Lithuania at greatest risk.
Another would be to secure the southern coast of the Gulf of Finland, which would put Estonia at great risk.
The only reason to invade Latvia first would be to isolate NATO access to Estonia via land.
During the 1930's and early 1940's, Stalin did fear that the pro-Nazi Finnish regime was a threat to Leningrad.
One of Russia's greatest prides is its navy. Its greatest historic geographic, commercial, military, and strategic definciencies were a lack of warm water ports with direct access to the Atlantic, Pacific, or Indian Oceans.
The US feared that the Soviet Union's invasion of Afghanistan was the first step towards establishing a port on the Indian Ocean within the sphere of Soviet influence; presumably in Pakistan.
One of NATO's best vectors of land-based counter-attack would be through Belarus , from which they could pivot north towards Petrograd, east towards Moscow, and southeast towards Rostov-on-Don. Counter-attack from Finland and Norway could neutralize Petrograd, Murmansk, Arkhangelsk.
As NATO Nations are pre-occuppied with Russia, China could make its move against Taiwan and the South China Sea. The same as the Japanese attacking European colonies in the East Indies while European nations were pre-occuppied with fighting the Germans.
Any counter-attack would have to be well-planned, well-practiced, immediate, and overwhelming. Delay, hesitation, ambivalence, diplomatic dithering, and 'proportional responses' would play into Russia's strategy to invade, occupy, and hold.
Putin does not want peace. He wants power and prestige via re-conquest of former Soviet and Rusisan imperial lands, and taking advantage of a divided West that lacks resolve and hesitates.
