that sortof depends on what the russian does.
if defending against split, the russian should (imo) stack in bryansk, that way he will be able to stop the german from being able to stand next to the stack since he is split. so the german will acheave almost nothing in south. The russian can also keep his mobiles and a few inf in smolensk (as long as germany can’t blitz there in a good way), so that it is not that simple for germany to take and keep leningrad without essensially chaning his strategy to going north, in which case the main stack can move north too,
going north is probably best if the german is doing a limited barbarossa, so the goal is to just capture leningrad, keep norway safe and support italians in africa. probably a good option after a cheap sealion.
south is where germany should go if barbarossa is the main plan for how the axis are supposed to win the game. all those moneys in cauc and iraq/iran that can be taken cheaply when italian canopeners are in place is ridicolous,