Germany cannot hold Caucasus early in the game.
If it tries, all Russia has to do is take Ukraine with West Russia forces, cutting off any reinforcements, and take Caucasus with combined West Russia and Russia forces.
On the other hand, Germany has a very easy time smashing Karelia early. If Russia reinforces in Karelia, I think the Axis have an excellent chance of winning, as Germany smashes the Karelia stack with the Baltic transport, Norway, Eastern Europe infantry plus assorted tanks. West Russia will not have enough to counterattack (since so many units were in Karelia in the first place), and the Germans have seriously damaged Russia’s ability to trade territories from W. Russia - the Germans can even secure Ukraine with that weak of a Russia.
Leave Archangel and Karelia open with Russia; do not defend. That’s my recommendation.