The starvation of Soviet POWs was obviously a conscious policy. This is proven by the fact that once the Nazis decided to use them for slave labor in early 1942, the POWs stopped starving in such absurd numbers.
The Nazis razed various villages and cities in Eastern Europe, including Warsaw, without any kind of military justification. See e.g.
https://en.wikipedia.org/wiki/Destruction_of_Warsaw
Himmler described well Nazi indifference to the suffering and death of "other races," including Russians (translation by CODOH of all places).
"Whether other races live well or die of hunger is only of interest to me insofar as we need them as slaves for our culture;
otherwise that doesn't interest me. Whether 10,000 Russian women fall down from exhaustion in building a tank ditch is of interest to me only insofar as the tank ditches are finished for Germany.
We will never be hard and heartless when it is not necessary; that is clear. We Germans, the only ones in the world with a decent attitude towards animals, will also adopt a decent attitude with regards to these human animals; but it is a sin against our own blood to worry about them and give them ideals, so that our sons and grandchildren will have a harder time with them. When somebody comes to me and says, "I can't build tank ditches with children or women. That's inhumane, they'll die doing it." Then I must say: "You are a murderer of your own blood, since, if the tank ditches are not built, then German soldiers will die, and they are the sons of German mothers. That is our blood."
Regarding the location of the main death camps - they were in Poland, because that is where the vast majority of the Jews killed in the camps were from. Poland made obvious logistical sense in a way the Netherlands would not have.
Nevertheless, there was a camp with homicidal gassings liberated by the Western Allies - Natzweiler.