Did German guards have a choice whether to work in concentration camps?

Answer 1

Not really. Most concentration camps were run by the SS. The SS had a military wing, which was like another army besides the ordinary German Army, and fought alongside the regular army (the Wehrmacht). Another part of the SS had the Einsatzgruppen which followed behind the German armies as they advanced and slaughtered people, and also ran the camps where people were sent to be either killed immediately or worked and starved to death. Himmler, the head of the SS, was extremely concerned about the effects on his SS men from having to murder all these people. Not for the victims, but for his own murderers.

Most people who joined the SS were very fanatical Nazis. At least in the early days, before the pressures of the war caused standards to be lowered, a man had to provide genealogical information back eight generations when applying to the SS, so that there could be no question that he had any Jewish blood at all.

Who DID have a choice, even if it was a bleak one, was the collaborators from among the prisoners in the camps. These people worked for the Nazis, hoping they would manage to stay alive by doing so, and usually they succeeded in extending their own lives some months. Naturally these people were detested by the other prisoners. They were called "Kapos" and many were among the most brutal toward the prisoners, hoping to curry favor with the Nazis.

German Prisoner of War camps, as distinct from the concentration camps, housed captured military personnel. These were usually guarded by men too old or physically unfit for front line duty. They were generally okay toward most Allied prisoners, all except the Russians. Literally millions of Russians died in German POW camps, most simply being starved to death.

There were also about 150 or so work camps, as distinct from concentration camps. These were by large factories and served every major German industry, including many firms still in business, such as Mercedes, BMW and Krupp. These "workers" were mostly people from countries the Germans had overrun, taken from their homes and forced to work in German war industries.

Every single German farm of any size also had foreign workers, also basically kidnapped. German agriculture ran on this slave labor, as all healthy German males were in the service. Every single German farmer was complicit. It was still better to be on a farm than in an industrial camp, because you might be able to steal some food. As Allied troops moved into Germany in 1945 they freed these agricultural slaves as they went, with the result being that nobody planted a crop in Germany in 1945. This resulted in widespread hunger and starvation among the German people in the winter of 1945-46, something which the neo-Nazis and Nazi apologists and sympathizers point to with Horror, as though it were deliberately done to the Germans. None of the Allies, having seen the way German food production was organized, were too sympathetic at the time.