There are many problems with ocuppations:
-When you occupy Germany, you get an event to decide what to do, if you decide to stablish a puppet regime the borders are wrong. The country doesnt get east prussia for example.
-When you occupy the Czech state and you decide to stablish a puppet regime the country simply never appears.
-When you occupy the kiel zone you simply cant decide what to do
-When you occupy Austria, the event appears after Germany´s one so if you decided to stablish a puppet Germany it annexes Austria aswell. So when the Austria event appears you can stablish a ppupet regime but only in a little province near Serbia.

As the Soviets:
-When you annex romania you should be given the chance of stablishing a puppet regime and taking Besarabia
-It will be great if you could negotiate with the finnish instead of just declaring war ( They are guarantee by Sweden)

Some things I THINK are wrong:
-When you go to the peace conference of WW2 you can occupy countries that capitulated to Germany (like France, Belgium...) So for example i was able to occupy France as the Soviet Union and i didnt get any event to decide what to do.
-When the spanish Civil War ends the Republicans peace out and stay in Spanish North Africa and join the Entente (I dont know if that´s a bug)


That´s my experience playing as the Soviet Union in the new update