But NAZIs had very gruesome plans
reduction of Local population through ethnic cleansing, starve to death, death in KZ.
until only 20-10% population survive as slave for Germans Settlers
we talk here about extention of holocaust to 65 MILION people
The more I think about real-life implementation of those plans, the more I consider them unrealistic as far as massive genocide ("65 mln Holocaust") is concerned. And the reason is actually very simple: it would be extremely disasterous for victorious Reich for very simple reason of European part of USSR as a whole being under- and not overpopulated. And, although Nazi proved that senseless killings to satisfy their racial theories aren't above them, I'm counting on regime dealing with Slavs in more rational way than with Jews.
Let's assume Hitler's wet dreams came true, Communist system collapses under weight of it's own sins and victorious Germany establishes control over Urals-Caspian Sea line (this strikes me as much more realistic than arbitrary AA line and gives Germans control of Ural industrial region, "Ruhrgebiet" of Russia, plus large swath of sparcely populated no-mans land between Volga and Urals to act as a buffer in case that "Siberian Republic" ever becomes adventurous). After some period (I would say "two winters", give or take, and within that period occupational forces would be too busy to carry out Slavic Holocaust) of initial mayhem Germans established reasonably firm control over the territory and started to implement Hitler's colonization dream. Now what? They have pretty substantial heavy industry and some rich mineral deposits to exploit (known but unused at this point, like Estonian shales, for example), plus all that agricultural land to re-settle "Race of Masters" on. Some areas of Central Russia (roughly within borders of medieval Muscovite Duchy) do suffer from agrarian overpopulation. But even those areas have underdeveloped urban areas. But a lot of places are underpopulated (I'm talking about Southern Ukraine, Lower Volga and Northwestern Russia, latter being conditional on implementation of modern agriculture). So, would Germans want to have a workforce to tile the land, it would absorb much more people than they can imagine.
And then there's a "little" matter of industry. Yes, Hitler did not plan to create Reich's powerhouse in Russia, but can Germany ignore the mineral wealth of the region? And now, once you dug the stuff out, isn't it natural to process it locally, rather than haul it across half of the continent? So, OTL industrial areas of Ukraine (which are powering Ukraine today, pro-Western region being heavily subsidized agricultural backwards), Russia (coal and iron of Southern Russia, wood and paper industry of Northern Russia, Lower Volga oil), Georgia (metals), Azerbaijan (oil) are more likely here to stay and often expand. And with them a lot of Slavic workers and some Slavic engineers. Some of Russian/Ukrainian/Belarussan workforce can be replaced by Poles cleansed from "Germanized" areas (Poland did suffer overpopulation to a much larger extent than the USSR). Now, fate of educated Russian class would be pretty grim. They would be reduced to lower positions under German supervisorship and their chances of career advance would be nil. However, it is still far cry from "65 mln Holocaust" thing. I can imagine pretty complicated system of ethnicity-based career opportunities, with Germanic peoples (Netherlanders, Scandinavians, French) and Italians being just one step under "true Germans", Hungarians, Czech, Romanians (a lot of them would likely move to "Ostland", either in search of career and/or business opportunities or to escape Germanization of their homeland) and Balts (who would likely be Germany's primary enforcers, with Nazi ideologues never being able to determine their proper position in racial system) occupying intermediate slot and Eastern Slavs being reduced to oppressed (but not actually genocided) group of forced labourers. However, Russian "high-tech" of the day (aircraft and machine-building industry of Moscow, Leningrad, Kharkov, Kiev, Stalingrad etc.), as well as education and R&D centers would likely be wiped out, Reich does not really need Russian science.
Now, back to $100,000 question. Can Germany ignore the Russian agricultural and mineral wealth and actually stun development of those territories to Hitler's idealistic vision of quasi-medieval network of baronies, employing Russian slaves? I don't see this as particularly likely, given that *EU (Germany-led European Union ITTL) would be locking horns with USA-dominated Western Hemisphere in *Cold War. Nazi-led Europe would need to exploit it's resource to a full extent to maintain parity or near-parity with America, and then there's a "little" matter of Siberia (it would have much more numerous population and solid industrial base plus unlimited support of USA ITTL, so it could become a big pain in German behind by 1950s).