Chemistry everthing from NCERT. Even in Jee Advance, many people say NCERT is good enough for 50%(which is huge). Organic is something which can be done from class notes or your material. I dont know about Doprep. It is regarded as one of the most relevant mock tests oit there. I havent attempted it yet. Remember the names and products of the reactions. GOC basics should be clear. And there wont be many wierd( Bitsat does ask 3-4 questions that cannot be solved and require high level of rote learning, like some scientist name or some other thing like that, just ignore such questions).
Also regarding bonus, go for it only if you have left 5 to max 10 questions. Make educated guesses in such questions. Make sure you have at least 15 minutes of time left. In mocks focus more on accuracy.
English and Logical Reasoning is known to be easy and it is easy. You can attempt all( in actual exam ). Chemistry and Physics, apart from 5 questions, rest are fairly easy. Maths is the deciding factor. If you find a question that takes more than 80 seconds, just leave it. Never think this is my strong chapter and need to do it, the control of not doing is most important in Bitsat. Apart from 10 questions ( which you should leave). Rest 35 will be in your finger tips. People waste time in one question and have to pay for it.
Another important experience, dont know about mocks, but in actual exam you must attempt the 40 questions of chemistry in 30 or less minutes, Physics in 45 minutes. English and Logical in 15- 20 minutes. That gives you 85 minutes for maths. Normally I do Maths last especially in Bitsat. Reason being that if I get the flow and am getting answers, then I may complete the section in 65-70 minutes, that gives me 15 minutes to go for bonuses( provided rest of the paper was great). However if it takes me more than 70 minutes in Maths, then I will make a decision and stick with doing thosr 150 questions only. Believe me, bonuses can be a trap for many students, you hear many people attempting bonus and you get tempted. But you have to adjust and make a decision before the half an hour or an hour is left judging by your paper.
This is my personal strategy after giving more than 20 Bitsat mocks last year and an actual Bitsat exam. No need to follow this. Make sure when you give mocks, you plan your own strategy. And improve upon it by every mock tests.