CSAB 2019(Central Seat Allocation Board) is the special round seat allocation in NITs , IIITs and IIEST Shibpur and some other gftis. This csab round is done after the josaa 7 rounds and it's main aim is to fill all the remaining seats in the colleges. It is also done in 2 rounds.

With your rank it is quite difficult to get NITs or IIITs but you will get branches like biotech, ceramic,plastics in different nits but is not advisable

https://engineering.careers360.com/jee-main-college-predictor

This is the college predictor you can find every ans. To your queries

All the best!!!