I'm currently studying the AQA reformed spec, but I would say that revision for Chem and Bio would be almost exactly the same within all exam boards
Honestly I think it would be really helpful to revise each sub topic as you learn them in lessons. Make notes as soon as you cover the content in lessons, which ensures that your revision notes are all fully prepared whilst also consolidating your knowledge learned during the day. This refreshes your memory and means it will last longer in your mind
by revising as you go along, you will be more relaxed during exam season since you will have more time to prepare for exam questions. I find that the sciences often repeat questions, sometimes changing certain examples, but generally the style and structure of the questions are the same each year. Therefore PRACTICE QUESTIONS ARE KEY! Haha it's honestly so useful to do a lotttt of past papers since you're more aware of what the exam board expects you to write
I'm a very visual learner so I like drawing mind maps, flash cards, posters, watching videos... I find it helps my memory retain itself. For chemistry, I recommend CrashCourse Chemistry, Allery Tutors, Khan Academy and Tyler DeWitt, all of which as on YouTube. For biology, CrashCourse Biology is very useful. Also there are videos made by My A Level Biology (the man who made the my GCSE science videos started A level Biology videos too) but this is specifically for AQA. I'm sure the concepts will all be similar though, just check your spec! I think that watching videos allows you to visualise the concepts learned in lessons meaning it's easier to remember
you can also watch videos at any time, for example if you're in the car to school each morning you could watch some revision videos.. In terms of revision websites DocBrown is realllly good as well as ChemGuide.
Most importantly i think it's important that you use your specification as a revision checklist. Thoroughly analyse the spec, since this is everything you're expected to understand. Highlight areas you're weak on whilst also ticking off subjects you've thoroughly covered in revision. This method was so useful during my GCSEs
Good luck in your exams! I'm sure you will do amazingly well