So the Nort Sout Corridor has 3 bypasses the western, the Caspian sea (central) and the eastern. Azerbaijan was never a trusty player that’s why the western corridor was kind of forgoten, on shouldn’t espect much from it or even from Armenia, which also has no train connection with Iran or even Russia. The western corridor was always to be limitative as some merchandises are forbidden to come from Azerbaijan into Iran, like oil products, and Azerbaijan also blocks the passage of other products.

The maritime route through the Caspian Sea has many bottlenecks. The traffic from this route more than double lately, the Ankhelansk port has not enough terminals, warehouses for such a volume of trade. There are needed more boats and the volga river needs to be deepened. This route is though specially important because it may allow maritime transport to the black sea using the volga-don canal.

The big star is the eastern route that already existed but was not explored. It allows continuous trafic on rail tracts from Russia to the Iranian ports in the indic ocean.
Last but not least the train track from Iran to Pakistan could actually be the key, it exists but it is terribly managed, not to mention that Pakistan cut off its rail connections with India. The eastern route is also interesting because it also connects to Afghanistan and allows a connection to west China.