I think without the war, "extermination through labor" would work very differently. The Nazis wanted "slave races" to work for them, and you do not kill slaves.
Don't get me wrong, they wouldn't be well fed, not at all, but there's a huge difference between a "slave race" the Nazis plan to rule over for generations and death through labor as implemented in the concentration camps. So the Jews, Roma, Homosexuals would be exterminated as during the war, similar with the Eastern elites, which starts with university staff, journalists, politicians and the like but goes on with teachers and priests. Effectively, everyone they'd deemed unfit to be an Untermensch of the new Reich or to dangerous to be an Untermensch. The rest would lead a pityful existence as the re-educated slave races of Nazi Germany.
The Nazis wanted a
limited number of long term slaves, mainly in General Government area, mainly very young, who could be brought up in conditions similar to those found in the Antebellum South (kept illiterate, raised to be chattel, etc.). Older people (which was anyone over about 35, although it would have varied by local Gauleiter) were going to be wiped out. Hitler was utterly serious when he talked about eliminating the Slavs.
Read
Generalplan Ost. The plan was to eliminate 85% of the population of Poland and Lithuania, 2/3 of the population of the Ukraine, 3/4 of Russians (60% killed, 15% transported to Western Siberia) and Belorussians, half of the Czechs, Latvians, & Estonians. The Plan would have taken 25 years, but the goal was to clear all of the East for fresh settlers, leaving 14-15 million slaves. The Plan talks about relocation, but relocating 100 million people is a fantasy (much like the idea of relocating the Jews of Europe to Madagascar), especially when one reads of how "Slavic" cities were to be obliterated so that no evidence of the existence remained, and how Saint Petersburg/Leningrad was to be razed and replaced by a massive lake, all the work to be done, by hand, by the local populations.
There is a general, usually unconscious, effort to mitigate exactly how utterly evil the Reich and its leaders actually were, putting them into a "sick bunch of (*&^%$, but you know, Stalin and Mao were almost as bad" category. IMO this is because the average person's mind recoils at exactly how far the Reich planned to go, was willing to go and meant to do once they won. Because of this the Holocaust tends to get all the attention because, as horrific as it is, it is something that one can almost get their mind around in the "Nazis = Antisemitism" sense. That the Nazis intended to murder over 100 MILLION people, literally because they were in the way, is simply so far over the top that it is unimaginable to most people.
Fortunately the Nazis were stupid enough to have actually written
Generalplan Ost out and made sufficient copies (including almost 4 MILLION copies of pamphlet describing how to identify the sub-human elements of the population) that they were found and are available for review.
Studying the Nazis plans is one of those efforts where every time you think you have seen it all, an entirely new stack of terrible appears.