In order to score good marks in BITSAT it is very important that your concepts should be clear and you should have strong fundamentals.You should read NCERT books throughly.
Yes, Arihant book is good for your preparation. It is very good for chemistry preparation.
For Maths you can also go for RD Sharma and for Physics you can go for HC Verma and IE Irodov.
To score good marks it is also very important to refer previous year papers and mock test series for your practice.
Questions in BITSAT is generally application based if you are well prepared for JEE Main exam you can easily crack BITSAT exam.
All the best!!