The game I’m running right now (hopefully finish tonight) the German/Italian player did a strict Barbarossa after conquering France and the results (in the Atlantic at least) were awesome. Granted, there were a few odd factors, like.
-British Med fleet making a run for the Pacific
-Getting Advanced Artillery on G2, effectively making the mass infantry stacks in the East a LOT more dangerous on the offensive.
-Italy effectively assassinating Brit income in Africa/Mid-East.
-Very successful Battle of Britain on G2 (trading fighter for fighter and rolling a 5 and 6 with both strat bombers against the factory)
As far as buys and deployment, the German left a sizable armored force (~5 tanks) supported by infantry and artillery in France with some small infantry stacks along Normandy/Holland supplemented with all of his fighters. In the East it was all Tanks/Mech infantry builds (I think he may have bought a tac bomber too)
As for the operation itself, the kick off wound up being G4 and there was probably some crazy luck with that too (in the massive initial attacks the Germans lost only three infantry). Afterward it was a matter of steamrolling armored forces across Russia until Moscow fell.
The war on my front (Japan) has been an absolute shambles though, despite conquering Calcutta…