HI,

YOU can apply for both IITS and NITS accepting your score.

Basically this depends upon ranking and cutoff for the session instead of marks, higher the difficulty level of paper-lesser the marks required to make good ranking

well it depends on the IIT you are going to, and the branch that you are trying for, and the category you are from.

The cut-off scores of various IITs, NITs and other good Institutes for post graduate programs. These cut-off scores will help you to set a goal which you need to achieve for getting admissions in the respective institutes

here is the link below to check out more details of which IIT or NIT ACCEPTING various scores

https://www.geeksforgeeks.org/gate-marks-needed-to-get-into-iits-nits-etc/