Please correct me if I am wrong, but basically the shape was dictated by two factors. The prototype was a concept a/c and as such used as many ready parts as possible and it was forced to rely on weak engines. Last but not least, reality forced any bomber development to the background.
After writing the above I decided to double check and hence to quote Manfred Griehl (p. 287 of
Jet Planes of the Third Reich Vol. 2)
Since no practical experience on the behavior of the novel swept-forward wings existed, Junkers engineer in charge of prototype construction, Dipl. Ing. Ernst Zindel, decided to improvise a flying testbed in order to begin flight trials in the shortest possible period.
If you wish to learn more about the design and its influence on Soviet aircraft development, you should look for
Deutsche Spuren in der Sowjetischen Luftfahrtgeschichte, by Dimitri A. Sobolew (I believe it has also been translated to english).
The Atomic bomb side I cannot comment on.