For your main question a lot of people thing senca is trash but it is really not i used senca so much during my GCSE's and i still do use it a lot in a levels, i used it for all the sciences in GCSE and i take all the sciences for a levels as well and i think senca is a great way to memorise the content as it is more fun and interacting to learn form it and the cram mode is literally so good, the amount of content you can revise with it is so good!
Plus the cgp books are literally a lifesaver i literally used them to get 9's in all three of those sciences, there is like not irrelevant info on the cgp book, and it directly links to the way the papers want the answers like if you revise the content on the cgp book the way it is written you will get good marks on the exam questions.
My way off learning is a lot different to people, i am a reader and hate making these "stupid" flash cards and mindmaps they are actually useless to me,(people say those flashcards and mindmaps help but i reality your making them and wasting your time trying to make them look pretty and such rather that actually taking in the info),(plu if you want mind maps there are pre made flash cards and mind maps on
https://www.physicsandmathstutor.com/ , there is flash cards for each topic and mindmaps), i love just reading over my content and then coming back to it and reading it again and again and after like a few days that content will be stuck in my head, by using a space repetition method like even my teachers dont credit me for my method they allways say dont just read its not good method, but i always prove them wrong. But the main part with reading, is the thing you do after this is want got me 85+ marks on all the science gcse's i did this year. You need to do LOTS of past paper question i did EVERYTHING i could find, because every year the questions are very similar and just the wording is a bit different if you learn the content and how to write the answers like the way the markscheme wants you to, the questions are so easy!, literally as soon as you see the question you will know exactly what to write! hope that helps!