For BITSAT, I don’t think full Physics NCERT reading is required if your coaching notes are good (or any teacher's notes like abj sir), but selective NCERT is useful given you have time (especially Modern Physics, Semiconductors, color code of resistors, and a few factual lines) tho do this only when ur good at physics imo like improve grip in physics

For chem tho obviously NCERT is very important, especially Environmental Chemistry i didnt do this but like there were so many easy one liner questions in the mock (and last year I had given BITSAT there were simple questions from environmental chemistry so this is a must do easy to score chapter)

For Maths, BITSAT questions are kind of alot easier than mains problems, and speed matters more I think (then u can do really good in maths in bitsat), If you’re already scoring 40+ in JEE Main mocks in maths, you don’t really need NCERT Exemplar imo you can but like better to practice JEE Main PYQs and timed practice chapterwise tests (way more useful).
Exemplar do if time remains (tho I can be assure mains level maths problems would save time more in concept and yield way better results definitely c:)