Which are the best colleges in South India for electrical and electronics engineering that I can get on the basis of 70% in class 12th?

Why not you try for UEM-Kolkata, the best you can find and have good placement record. Visit the link to get acquainted with courses and fee structure: https://www.shiksha.com/university/university-of-engineering-and-management-kolkata-47398

There is no good engineering college in south India offering admission on the basis of 12th score.