What's the difference between Toshiro and Ichigo's Zanpakuto lore?
Zangetsu wasn't suppressing Ichigo's powers nor was he hindering Ichigo. Zangetsu only feared that Ichigo would come to him to learn the Final Getsuga Tenshou. Zangetsu didn't want Ichigo to become a Shinigami, because he (and Ichigo) was part Quincy (and not to mention, Hollow as well).

The reason why Toushiro and Soujiro had the same Zanpakuto was explained in the anime. Go watch it.

Ichigo always had the ability to become a Shinigami because he was part Shinigami (from his father). Since his mother was a Quincy, he could have been one too. He could've become a Hollow if he wanted to. Rukia and Urahara only sped up the process.