I don't know the rules for basic training, but you get the choice of trousers or skirt in the 'real' RAF.
You need to be comfortable with communal showers and being naked in front of others. The sports facilities after PT are communal showers and so is some of the accommodation. You will also be in shared rooms for training.
This gets more important should you deploy as part of your job. You NEED to be able to live very closely with others for periods of time and that includes eating, washing, sleeping, working.
The tests are hard for some and easier for others, the same as any exam or test. Some people get A's, some get C's, some fail.