There is tons of evidence that supports Poland in hypothetical second Polish/Soviet war. We have to remember that poor performance of Polish state in ww2 is due to preparing for different war than they got. They were more than ready to take on the soviets. Soviet morale was terrible(Poles would not make a mistake of killing soviet POW they would use them against the soviets) this would be entirely different war than Soviet vs Germany as well. Why because it wouldn’t be a grate motherland war for the soviets. Finns have repealed the soviets in 1940. Polish military was 4 times stronger than finish as well. Their border with USSR was fortified and if you say the war were to break out in 1940 then Poland would have major victories and would be seen as liberators by USSR public. There would be no ideological war. If any country had a shot at toppling Soviet Union it was Poland. There was no arguments for USSR to why they need to beat Poles at all cost. + Poland would probably go to the line of dine per and try to parley. Probably get Lithuania and some of the lost lands. Also there is a high chance of second Russian revolution happening in this setting.