I’m a UK Strategist from Crimson, thanks for your message! For Oxbridge, they definitely are looking for candidates with genuine passion towards their applying course as well as the academic potential to succeed afterwards in the degree. So your extracurricular activities definitely help to demonstrate your interests as well as the well roundedness of your profile, ideally subject related.
As to how much Oxford cares about the TSA Essay section, you can imagine most candidates applying to any of the Oxbridge degree programmes all have strong academic predicted/actual grades, admission tests, in this case TSA for Oxford PPE, are definitely a great way to stand out and differentiate yourself among all the candidates if you are able to do really well. This is also an important benchmark for Oxford to judge on candidates’ academic ability as students are all from various different curriculum and backgrounds around the world.
I hope this help answering your questions.