which jain sect have highest following population

Among the two main Jain sects:

• Śvetāmbara (Shwetambar) – has the largest number of followers worldwide (roughly around 70–80% of Jains).
• Digambara – has a smaller population (about 20–30% of Jains).

Within Śvetāmbara, the Mūrti-pūjak (Derāvāsī) sub‑sect is the largest by population.

You can read a bit more about Śvetāmbara and Digambara sub‑sects here