I got 98.7 percentile in jee main paper-2(b-arch) and my category is OBC.can Is it a better score?what nit's can I get based on my percentil

Definitely 98.7 percentile in paper 2(B. Arch.) of JEE Mains is good score you can surely get a nit with this score. We cannot predict which college you will get as closing rank of different college changes every year so  you can go through the list below and check for your favourable college

Malaviya National Institute of Technology, Jaipur

Maulana Azad National Institute of Technology, Bhopal

National Institute of Technology, Calicut

National Institute of Technology, Hamirpur

National Institute of Technology, Patna

National Institute of Technology, Raipur

National Institute of Technology, Rourkela

National Institute of Technology, Tiruchirappalli

Visvesvaraya National Institute of Technology, Nagpur

You can also predict your college with the college predictor

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