Dear aspirant,

According to your question and taking into consideration that you want to know if jee mains level of physics and chemistry is enough to score 90+ in kvpy SB stream.

I would like to tell you that jee mains and kvpy both require different strategies to clear the exam and so the levels cannot be compared as the time limit for both exams are different.

But in general if you are fluent with jee mains then you can also hope for kvpy.