Picking a role based on how easy it is to get into is NOT the way to choose a career that you could be doing for up to 20 years, potentially. And not a discussion that is expected for an 'in-depth knowledge of the RAF'.
Selection isn't easy for any officer role, but it varies as to whether it's because of the requirements or the individual; some roles require particular mental skills and coordination, some roles have very exacting medical or fitness standards, some people struggle with the Filter Interview or at OASC no matter what they are applying for.
Pick a role that you are interested in doing. If it's challenging to get into, so what? Being in the military is challenging and you're not always going to be able to take the easy option.