IMHO - the best option to take Leningrad was earlier - before Zhukov took overall control of the city. If there was less interference from Hitler (hold there, wait for the infantry to catch up), and OKW insisting on attack routes, rather than the guys on the ground who could see the lay of the land, and act quickly before the Russians had a chance to react.
If German units suddenly entered the outskirts of the city, would the result have been any different to that of Minsk & Smolensk, that went before!? Without the 'iron hand' of Zhukov who would ensured that the line was held.
Not saying it would be quick, after all it's a big city, but I don't think it's ASB that to have fallen earlier.
It would bring large benefits to the Germans - logistical supply hub via merchant supply ships. Not so good for the people left behind!!
Moreover, if they could sever the Northern L-L supply line, that would make a big difference.