How do we distinguish between sects that claim to be on the correct methodology (Manhaj), especially with the proliferation of other sects mentioned in the Prophet's Hadith that there will be 73 sects and only one will be saved? And how can we refute them and distance ourselves from them, with evidence from the Quran and Sunnah?

Disagreement and disunity within the Ummah are inevitable and appeared early on. However, Allah made the divergence of sects an emergent phenomenon distinct from the creed of Ahl al-Sunnah wal-Jama'ah, as mentioned in the hadith about the Ummah splitting into 73 sects, only one of which will be saved. The saved sect is the group that follows what the Prophet, peace and blessings be upon him, and his companions were upon, and it represents the vast majority of the Ummah's scholars. As for the doomed sects, they are the misguided and innovative groups that contradicted Ahl al-Sunnah wal-Jama'ah in fundamental principles and overall beliefs. However, most of them are not considered disbelievers, unless they explicitly apostatize from the religion with clear disbelief, like the extremist Rafidah and the Batiniyyah. If groups differ in methods of da'wah (invitation to Islam) but do not contradict the creed, they are not considered among the doomed sects.