Main problem is this, after Czechoslovakia, any German expansion will cause WW2 period. Germany has used up all its credit and appeasement is totally discredited by the end of 1938. So no WW2 means pre 1939 boundaries.
This brings up two issues that relate, first its continuing treatment of Jews/Slavs/Gypsies/Communists/Handicapped etc was/would cause sanctions/embargoes/boycotts from other nations. The persecuted can try and flee but this is the 1940's, no one will take many ( even the US was turning ships away ) so they mainly will have to stay put and suffer so creating more and more bad press.
The German economy was in a bad way by 1938. Hitler was building a lot and creating a false boom by use of internal IOU's and confiscation of undesirables assets, this can only continue so long. Add in the embargoes , sanctions and boycotts and Germany starts to implode by the mid 40's economically. Tanks and planes are great but they don't produce food or heat.
So we get to say, 1942, popular unrest is growing due to the economy, the military is basically just maintaining what it has whilst all the other European powers have rebuilt their militaries. Stalin has got all he wanted out of his pact with Germany ( machine tools , tech , equipment etc as Germany will have had to substitute these for money) and has no need to be nice ( as much as he every was ). So Germany would lose if it attacked anyone rather quickly ie WW2 by German aggression is probably over as an option.
Longer term, either the Nazi's fall due to internal issues or they go into a repressive tailspin leading to ever lower economic performance compared to everyone else ( think North Korea ). WW2 is then avoided but the Reich is a third world country which like the USSR falls apart as soon as it cannot repress enough.
