No, To get admission in DTU or NSIT through PMSSS JK you don't have to even appear for JEE mains, your 12th marks should be very high to get seats through pmsss. In this case, AICTE will pay the college and hostel fees which you might be already aware of.
But if you are not applying through PMSSS and want to take admission through JoSAA counselling as other students take then you have to appear for JEE mains and get good score in it. In this case, you have to pay the fees yourself. You can also apply for PMSSS even after clearing JEE Mains if you did not get the college through the choice filling.
AICTE JK PMSSS also supports scholarships for students who clear National level entrance exams.