I'm not sure whether I have understood your question, but let me try to answer anyway

:
DD and Arma are complete upgrades, i.e. once you have those installed, you can take your original HoI2 CD, brake it in half, trample on it, burn the remains and then throw that mess away.
The AI was among the major improvements of both DD and Arma, and with the Armageddon 1.3beta2 patch it is the best you will ever see without modding. Just install Arma, the 1.3beta2 patch and then start a 1936 campaign - you will be satisfied.