If you pick Poland they'll have a huge norder with the nazis. This gives you both their cores and their 8-11 Divisions. If pick Austria you'll get an event that lets you Anschluss them after some time. There are only two senseable options: Poland or Austria. You can pick one non-aligned country to create a faction with. This moment right before the first shot of the war is fired is actually quite valueable, because you are now a non-aligned country without a faction. You have half your army vs the other half, although you should have more factories and manpower (especially if you conquered something beforehand, just don't puppet or ally anything under hitler).
If the civil war triggers you should instantly pause.
The landsturmregiment exploit is basicly cheating you all equipment you could ever wish for and all other exploits seem to be fixed in 1.9.1, so I recommend the honest way.