Are hand drawn 2D shapes acceptable or the meaning here is to utilize the existing sprites shapes in each engine?  

The Hand drawn shapes will look similar of course to the actual shape, for example

i don't know, but last Jams every one submitted with engine sprites. So probably you should go with engine sprites. But if you do submit it with hand drown shapes I won't ban your game. But, other people might not rate your game that much because you did't you engine shapes.

so Engine sprite shapes :)

your choice :)