I found the way I used my EPQ log to be very useful (useful enough for an A*!). Basically, you should be gathering evidence from multiple sources like journals, books, websites, videos (all credible ofc). You put them into your source table, and make a note of what's useful/if you agree and evaluate it. You then use your notes from this to write your essay and cite them in your essay (important so that you don't end up accidentally plagiarising!). Keep all of the sources you find in the table because you it will show off all of the research you have done. Your project log is marked as well as your essay, and you can get a lot of marks from this- so evaluating how your project changed and showing that in your table can get you marks. Your EPQ is submitted as your essay, production log and any other resources you used to help you with your project (like gantt charts). Hope this helps!