Based on your previous board exams performance you are already a top performer and you don't need to doubt yourself and your preparatons.So ,NCERT textbooks are the basis on which the questions are fromulated ,so you need to go through it while you can use additional maaterilas to widen your knowledge but don't try to skip NCERT as it is the foundation.Stop doubting yourself,kick start your preparation,I see a board topper in you.Hope you will not disappoint us.

What's ur stream?? That's depends upon ur understanding

Absolutely. CBSE board exam is based completely on your NCERT textbooks. If you are thorough with each and every chapter from NCERT books, you will definitely score well. Read word to word, workout every exercise of the chapters as well as solved examples too.

Preparing from anything other supplementary books will help you prepare for entrances too.

No

.Ncert is not sufficient For 12 Board ...We need to prefer Some Extra books Like ACCOUNTS  OF  Ts grewel ..Bst of Poonam gandhi & Eco of Sandeep Garg..