Interesting question, Spencer.
I would want you to look at these (Week 4: Identity cat / non-cat pictures) & (Some Experiments with the Cat Recognition Assignment (C1W4A2) - #3 by paulinpaloalto) first, to understand how are we training the model through different set-ups.
The week 2 assignment was simply using logistic regression as a medium without using any hidden layer. But in week 3, we do apply one hidden layer. The task gets complicated here because we don’t have much cat pictures available on net. In that case, we need to synthesise them through the process of data augmentation.
The rest of the of the explanation given in those links has been well justified by Paul sir. Let me know if you get an idea and we can always have them discuss over here.