Hey

Securing at max 20,000 All India Rank in JEE Mains would be preferable to get admission into NIT, no consideration to branch . The better you score, the better branch and NIT you would get. With maximum required rank, you would get new NITs like Manipur, Sikkim, Sringar etc.

For that scoring at least 97 percentile is must being a General Category student, and you would get a bit relaxation if you belong to same state as that of NIT. A score of more than 120/300 would be safe.

For further doubts, ask us.