Since your percentage is below 75%, you cannot take admission in NITs/IITs/GFTIs. But obviuosly there are many other institutes in which you can take admission like you said NSIT, DTU etc.

NSIT:

JEE Mains AIR is the basis for admission in NSIT. 85% seats are vacant for the Delhi Region students. And, candidates who pass the qualifying examination from a recognised school within NCT of Delhi will be considered in this category. 15% seats are for other students.  Candidates should have a minimum of 50%(OBC) aggregate score in Physics, Chemistry and Mathematics. And shpould have passed English to be eligoble for admission in NSIT. There is no age limit for admission in NSIT. 

DTU:

For this you have fill the form on DTU official website. Minimum eligibility is 60% in aggregate of Physics, Chemistry and Mathematics along with English as one of the main subjetcs. Candidate's age should not be more than 25 years. Here also, 85% seats are reserved for Delhi Region Students and 15% for those outisde the Delhi. Final admission is based on JEE Mains score followed by Joint Admission Counselling(JAC). 

Jamia Milia Islamia:

They also take admission on the basis of JEE Mains score. Candidates must have passed 10+2 with Physics, Chemistry and Mathematics with atleast 55% aggregate score.

Still, You have many options in fornt of you. You can also apply for State Engineering Colleges. There are many States institutes providing good infrastructure, good quality education and faculty etc. And with good placement record.

Hope this will help you.

Best of luck 

Hii Vishal, the minimum percentage required for clearing mains is 75% and 65% for SC and ST category. So even if you have scored 200 in mains you will not be able to qualify mains thus there is no question of getting selected in any of the following colleges. You can give an improvement exam next year or select a college that does'nt give admission on the basis of JEE MAINS.

I hope this would have helped you. All the best!