I think you'd see a similar situation to China, where the territory known as Russia was 'nominally' a nation but it would have large numbers of warlords, some of whom might even attempt to formalize their holdings as seperate nations.
If China is the example, this would mean that a Unifed Russia would probably emerge in the late 1940s, possibly with a Capital city in the Urals or some such. In any case, the warlords in place would almost certainly be as irresistable to Hitler as the Chinese warlords were to Japan.
And like Japan, the Germans are going to get stuck in a massive vietnam-like quagmire. This would probably be followed in a prolonged campaign from the Western Allies as they force their way from Normandy all the way to Ostland and Ukraine, possibly with heavy nuclear weapons usage.
On the Japanese side, I'd expect Japan simply to hold the Maritime Province and Sakhalin 'for the duration' which turns into "forever". Sakhalin has some oil as well, not enough for the IJA's needs but definitely something that gives them some breathing room.
Now the postwar situation in Europe would probably have the Western Allies at the Ukraine and in St. Petersburg, but there would still be warlords past that point, along with a largely friendly Russian State emerging--Russia has lost some land, but St. Petersburg would probably get returned to them and the Russians probably join a postwar alliance.
Hmmm...