Al-Shafii taught in Iraq and then moved to Egypt, and he revised his positions after the move. The tradition preserves both layers and names them: the qawl qadim, the old doctrine of the Baghdad period, and the qawl jadid, the new doctrine of Egypt. Where the two conflict the new one generally prevails, and the later literature of the school spends real effort on the cases where the old position is nevertheless judged the stronger. That a school records its founder changing his mind, and keeps both answers in view rather than quietly dropping one, is itself a feature of how it works.
Two thirteenth century scholars fixed what the school actually holds. Al-Nawawi and al-Rafii each produced comprehensive works sorting the accumulated opinions into preferred and rejected, and where the two agree, later Shafii jurists generally follow. The Minhaj al-Talibin of al-Nawawi became the text that commentaries were written on for centuries afterwards, so that arguing with the commentary tradition is how a Shafii jurist argues at all.
The geography of the school follows the sea routes as much as the land ones. It is dominant in Egypt outside the far south, in the Levant, in Yemen and the Hijaz, along the Swahili coast of East Africa, among the Kurds, and across maritime Southeast Asia, where Indonesia and Malaysia are overwhelmingly Shafii. That last stretch means the largest Shafii population in the world is not in the Arab lands where the school was formed.