(Pole and Hungarian — two brothers, good for saber and for glass.)
Some countries in the EU have better relations than others. Czechs and Slovaks, the three Baltic nations, and Poland and Hungary. Things must get really bad before they will stop having each other's back on the international scene.
This is a historical and diplomatic fact that must be taken into account when conflicts arise.
That said, I would welcome a citation supporting this assertion. My personal experience is very different and I do not want to swap anecdata.
The common geopolitical interests - true as long as you believe Poland is more comfortable with the West rather than in "Eurasian Union". Nordic countries are way more liberal, but they are wary of Russia. Historically Russia was often in conflict with Poland. Scandinavian Peninsula can be a great obstacle to Russia if it wants to expand west. It threatens sea routes and airspace and it's only going to become more important as global warming makes the north more navigable (without icebreakers).
Hammer and anvil - alternate names for the location of Poland (and Ukraine) include Bloodlands(Timothy Snyder), crumple zone(Jacek Bartosiak). Russia and Germany are powerful states and many transport routes lead through Poland. The Carpathian mountains in the South and Baltic Sea in the north form a sort of a bottleneck. Timothy Snyder is of the opinion that central-east Europe had the great misfortune of lying right between two totalitarisms - fascism and communism.
This is a bit of contrast with Hungary, which is now completely inland and land transport is about 10x more expensive so it's not as good for trade.
Or do you mean the Finland? I can expand but you can find common points between Poland and Finland.
Can you expand on the Poland and Finland?
As for Finland, it's the more superficial things. Wars against Russia, desire to be independent, and Finland fought Russia very effectively in the defensive Winter War. Both Poles and Finns are heavy drinkers.
Since you seem to like this kind of books: Timothy Snyder is an US historian specializing in Eastern Europe, and he's especially fond of Ukraine. He also has good lectures on youtube, although I think he's trying too hard when he's commenting modern politics.
Norman Davies is an English-Polish historian with a particular interest in Poland. He speaks the language surprisingly well. The books I'd recommend include: "Red Star, White Eagle". He described an unlikely outcome when in 1920 Poland won a war against Bolshevik Russia, and delayed the onset of communism in Europe.
Poland has nothing to do with Orban and wants nothing to do with Orban. Unfortunately we have our own populists that like Orban wants to remodel our country to be easier for them to rule as they please. And results are similar as with Orban in Hungary and threats to that from EU are the same so cooperation against EU safeguards is kind of natural and spontaneous.