The real question is? Does the holocaust and great purge still happen? Dun dun dun.
It depends on how the Nazi' develop here as a party, are we getting kill/enslave all the non-aryans, or just kill the Communists?
Both Germany and the USSR are going to be stronger and weaker ITTL, the Soviets especially.
The USSR because although industrialisation is still happening (with complete disregard for human costs like OTL) and no purges (Old school generals from WW1 and the Russian Revolution probably won’t last against Panzers and Stukas anyway). The Soviet Government will be rife with bureaucracy and corruption, Trotsky’s Soviet democracy along with no fear of being purged means people juggle for power a lot more which might slow down modernisation, not to mention the cost of exporting the revolution which will most likely be put down.
Not really. The USSR, without Stalin, is a very different beast. No Stalin means do destruction of party democracy, as your going to people who aren't just Stalinist stooges. As for no purges, you are really underestimating the Red Army. The Red Army would know first just how bad tactics from the last war were, so you bet the Soviets are going to modernize. As for exporting the Revolution that never really happened under Stalin, save Mongolia and Tannu Tuva. Stalin cared more what the Soviets could gain now, it is why he pissed over the idea of China. Supporting the Mongolians who technically separatists from China, a propping up a client state in Xinjiang, supporting the Nationalists against the Japanese, but did not really bother with intervening in the Second Sino-Japanese War.
Germany because two (and maybe later one, hint hint) strong leaders and masterminds in logistics and propaganda will guarantee the Nazi party stays in power from within (Not sure on whether or not to make this a Nazi Victory TL).
Stalin and Hitler are not the most stable of combinations, considering Stalin could have plenty killed over really petty reasons god forbid he gets something close to the Gestapo. A Nazi Victory TL is impossible unless your gunning for an alternate war? A German-Soviet War I could see, but WW2 but with Nazi Stalin is not going to work.
A big question is what are you planning to do with the rest of the world. It cannot exist in a vacuum but I could lend a few ideas if need be, but I need an idea of what kind of story are you crafting, and is it entirely feasible?