The SU at the start of the war had a 160 million population, the Großdeutschland 80 million
You cannot stack populations and nominal values (also the value for 1940 was 195 million, the population was also younger), thats the trait of an amateur, Qvist on the AHF made a good post about this, I am going to quote it:
It's not a question of how much more manpower they had, it's a question of how many more men they were able to feed into the campaign in the East. You can gain a fair understanding of that very simply. The Red Army started the war with less than 3 million men in their operational fronts and ended 1944 with roughly 6 million. In between, they suffered roughly 27 million casualties, which means that during that period they added some 30 million men to their forces - including, of course, returning wounded and sick. The Germans began the campaign with roughly the same number of men, and at the end of 1944 fielded roughly 2 million men. In the interval they had, what, 5-6 million casualties, hence added something in the vicinity of 5 million men over that period. You can even give or take a few million on either side, it doesn't really affect the basic issue. These were only procured with enormous difficulty and as a result of the conscription of millions of foreign laborers and the lowering of military age.
It is not remotely in question that the Soviet manpower stream in the East dwarfed the German - that is clear from the most basic data. It is only a question of accounting for how and why. On the German side, as already mentioned, they were essentialy already dry when Barbarossa started, except for the new age classes growing into military age and returning convalescents, which was entirely insufficient. They didn't need any additional drain from other fronts to be in trouble - when that kicked in, it simply made things even more intolerable. The key reason for this is that German industry occupied many million able-bodied men who could not be released without hurting armaments output or other critical economic activity. In this sense, other fronts was in fact already having a huge effect on the manpower situation, though mainly in the form of millions of workers devoted to supporting the hugely resource-demanding aerial and naval campaigns in the West and South. They were gradually tapped into as foreign workers were brought in, but Germany simply didn't have more than a few million more men to draft, additional to what they already had in the field in the summer of 1941, mobilised to the hilt as they were (given the labour resources they then had).
The Soviets did - for several reasons. Firstly, the USSR only moved to a war footing as war broke out - they could tap into the same sort of slack that the GErmans did on the outbreak of war in 1939. Their armaments industry was smaller than the German, the rest of their economy smaller still and living conditions was cut more mercilessly. The economy was generally less reliant on highly qualified labor, hence workers could more easily be replaced inexperienced labor. Women participated economically to a much greater degree than in any other combatant nation. The population was younger. Proportionately more men could be freed up for the military war effort, all of them could be devoted to the land campaign against Germany and they could be mobilised very quickly because the USSR had an enormous number of trained reservists. Eventually, lend/lease helped to buffer against some of the worst effects of the merciless plundering of the economy for men, for instance through food deliveries. As the RA went on the offensive and regained ground, they could - and did - draw on manpower from the liberated areas. It all added up.
In summation - the notion that you have two states with 80 and 120 million people both starting on square one and with a corresponding ability to devote new men to an ongoing war in the East doesn't survive any contact with realities of the situation. The Germans were severely pressed to come up with ANY significant additional manpower if Barbarossa couldn't be finished in a few months.
No, they did not pump out more armaments than the Germans, the overall volume of German armaments production was significantly larger, as was the overall size of the German economy. It was also a lot more diverse, which is why you get greatly superior Soviet output figures in the limited range of items they focussed on.
Hungary, Romania and Finland are irrelevant to the issue of German manpower. Finns, Romanians and Hungarians did not man German military units, nor German factories. Each of these states of course produced their own military forces, which to varying degrees made some contribution on the Eastern front, but that's a different matter. As well as a relatively marginal one. The Finnish front was essentially passive for nearly the whole campaign. The Romanians made a significant contribution mainly in the summer of 1941, fall of 1942 and spring of 1944, between which they fielded fairly marginal forces with limited combat power. The Hungarians were a factor only in the fall and winter of 1942, and again to a limited extent in late 1944. The contribution of these states to Axis combat power in the east was in no proportion whatsoever to their population, and it is entirely meaningless also for that reason to add those to the German general population. Again. This is the sort of thing that only makes sense as long as you are happy to operate in the fairytale land of cajoling historical meaning out of global demographics.
Sure I've derived it from the casualty data, and there is no problem with doing so, it is a perfectly valid method for assessing the overall magnitude of manpower addition. If you have 2 million men at point a), suffer 3 million casualties and end up with 4 million men at point b) subsequently, then you have neccessarily somehow added roughly five million men, including returning sick and wounded. If you didn't, then you neccessarily either wouldn't have 4 million men, or the casualty figure is wrong. Strength development + casualties isn't just a simple way of determining force addition, it is the definition of force addition.