Destroying the UK Home Fleet on G1 is sound strategy. Once accomplished, maintaining even a small Luftwaffe presence in Western Germany/France forces the UK to buy warships before they can buy transports and invade the mainland. If you’re bombing London every turn, the UK shouldn’t have a sufficient invasion force assembled before the Americans arrive on the scene.
When I invade the USSR, Phase One is a two-pronged attack, aimed directly at Leningrad and Ukraine. If you take those ICs, there’s no need to build one in Romania. Up until the turn in which I capture those two territories, I SBR them.
At that point, Phase Two kicks in: I shift the bombing to Moscow and Volgograd and advance on those territories. If the opportunity presents itself, you can ignore Volgograd and drive straight for Moscow, but I usually find the additional IC in Stalingrad really comes in handy. And yes, taking the more valuable southern Soviet territories should have higher priority than, say, Vologda or Smolensk. Caucasus is the northern gateway to the Middle East. Never forget that, while Iraq, Persia and NW Persia are worth 4 IPCs to the Allies, they’re worth 10 to the Axis.
Don’t forget to park a U-boat in sz 125 to deny the Soviets those 5 IPCs. Also, once Leningrad is yours, it should be fairly easy to send a small force blitzing through the northern territories to Novosibirsk and cut off that 9 IPC per turn flow.