There are two steps to getting an A/A* in Bio at A-level. 1) Know your content back to front. 2) Be able to apply it in unfamiliar contexts. If flashcards help you memorise stuff then that's absolutely fine. But for no2, PPQs are crucial and you seem to be doing those so that checks out too! I would advise against using other exam boards, however, because they may word things differently and stuff like that. If you somehow run out off PPQs Edexcel have loads of sheets and questions in their textbook which you might already have access to - if not, ask your teacher.
One last thing, if you're shooting specifically for that A* there's, you have to be able to draw together all your knowledge from across topics. I.e. don't think of the course as split into topics, rather, you're learning biology and all these topics intertwine. Doing PPQs, you'll see how the exam board forces you to bring together all your understanding - another good way to improve this skill is by doing supercurricular work for biology. I.e. read the occassional STEM article or biofactsheet. A good exercise could be to choose a heading, like idk, proteins, and see how many links you can make between topics. E.g. for proteins: protein synthesis, protein trafficking, cystic fibrosis, clotting cascade, facilitated diffusion, genetics etc. These will all help you think about biology more holistically as opposed to compartmentalised topics.