Hello,

Congratulations. With your JEE Advanced rank, you have chances of getting CS and ECE in some IITs in front of the colleges i have mentioned the 2020 ranks:

1. IIT Mandi  31
2. IIT Jodhpur 63
3. IIT Pallakad
4. IIT Dhanbad 12
5. IIT Goa
6. IIT Bhilai
7. IIT Tirupati
8. IIT Jammu

For BITs which is ranked 30, with a score of 305 it is difficult to get into  CSE and ECE, you might get stream like Civil Engineering, Chemical Engineering and Electrical and Electronics Engineering.

For NITs, with a rank of 18827, there are less chances of getting a seat in CSE.

https://engineering.careers360.com/articles/nits-cutoff-for-top-btech-branches

Your decision can be rank based, since you want CSE or ECE only and rankings are done considering many factors. But about BITs, you can consider other branches as well.