Don't do AQA they have one exam which is a 25 marker - that's a single essay on ONE question, you don't get to pick between multiple, there's only one choice. If you mess this one question up then you will get a bad grade... SO DON'T DO AQA!!!
Edexcel is better (also slightly lower ~5% 2022 grade boundaries) - there's Edexcel A which is more human health orientated and Edexcel B (I don't know what this is like but I'm guessing more biology in general related)
For the summer, consolidate on GCSE knowledge bcos A level just builds on that and teachers usually won't go through basics taught in GCSE again. Also buy revision guides/ flashcards/ textbooks early so you can revise throughout year 12.
TBH I do OCR A and in my opinion its the best as it follows really closely to the GCSE edexcel with a few new topics here and there