Hi! I see you're problem as I myself thought I faced the same.

What I would suggest is, keep your main focus on NEET. The syllabus of both is more or less the same, and their will be slightly higher weightage of the syllabus you have in class 12. Obviously, you'll have to know the concepts first. ISC is significantly easier than a competitive, so once you read the subject matter properly and understand it, you would be able to solve both MCQs and have the concepts in your mind. So prepare with your competitives in mind. The preparation for your subjects will be best that way. Two months before boards, start solving mock test papers, and that will help you to get in tune with the answer writing format for boards. You don't need excruciatingly good marks in boards to get in Medicine, but this way, you'll get above 90% for sure. In the background, keep practicing mcqs, except when the main body of the boards goes on.

Good luck for your exams pal!

You have to prepare for NEET exam alongwith with your boards.

You must give importance to those topics and sections which are scoring in nature. The best way to do is to analyze sample papers and previous year question papers. It is better to draw a matrix of chapters as per their weightage. It is a waste to devote time on chapters which are of less mark.

Studying NCERT Books thoroughly is the key for complete preparation. For additional help, candidates can refer to books from renowned authors and other study materials. NCERT Books are the base to get your concepts clear and strong in all the three subjects.

In order to develop a foundation of theory, you can take a lot of Mock Tests. This way you can develop a time management strategy and recognize your weak areas.

All the Best!!