Hi Divey – one thing is for sure, is that many, if not most, line up at the start of a race with some sort of doubt in their minds. The key aspect is to not put too much pressure on yourself and enjoy the event. It can take many tries before you nail your races. Look to gain experience and leave your ego at home. This is your hobby after all 😉
As for the training questions, I suggest you go with the SBR stimulus. Focus on becoming a better all-around athlete, as well to being consistent physically and mentally. Then once you have mastered that, you can “up the ante” with the training or focus on 1 particular leg. But don’t rush the process or set numeric expectations.
Think of each training cycle or “layer” of training as an opportunity to get a little better long term. It’s also important to be flexible with the training, don’t sweat the imperfections or expect instant results in training.
All the best and keep us up to date!