Trying to understand Ext.require, Ext.class.requires, and Ext.Loader - extjs

Question

So I've inherited this extjs 4.1.3 project and I'm trying to understand it.
I've noticed that there are both Ext.require and Ext.define requires EVERYWHERE. The code is made of a lot of boilerplate code from sencha docs and I feel there is a lot of redundancy. It makes a whole lot of clutter and I feel like its wrong that when I add a file, I have to add it more than once (to Ext.require and Ext.define requires).
Couple of questions:
1) How can I tell if a require is actually ... required? From my understanding, it only tells the web page to load something now or later (this might be related to question 3). Am I guaranteed to see warnings from Ext saying "you should include abc" if those files are needed?
2) Is there any difference between Ext.require and Ext.define requires? Do I need both? If I only need one, is one more "standard" than the other?
3) What exactly does "Ext.Loader.setConfig({enabled: true});" do? I am guessing that lets ext dynamically load things if I don't specifically require them. Shouldn't I not need requires at all then? I'm not saying this is good practice, but is it true? Actually, if anything, isn't using this bad practice? You'll end up losing track of dependencies if you don't have them written down. Or do you "trust" Ext.Loader to take care of everything relating to dependencies so that you don't even have to worry about it.
The reason I ask because I thought this was true, but after the below experience, I am thinking it is not.
I thought I figured this out, but apparently my interpretation of Ext.Loader (Question 3) is wrong because if I comment out all of my requires, I get
[07:15:05.577] Error: [Ext.createByAlias] Cannot create an
instance of unrecognized alias: layout.border
If I take out 'Ext.layout.*. How come this isn't loaded dynamically if have Ext.Loader.setConfig({enabled: true})?
TLDR: I don't know when it is safe/good practice to use Ext.require/Ext.define requires. If I don't see any warnings and my app works, does that mean I'm good or is there still a chance something is being "loaded" as well as it could be? And what does Ext.Loader.setConfig({enabled: true}) do?
EDIT: Here is an example: the app.js file. It just feels to wordy doesn't it?
Ext.Loader.setConfig({enabled: true});
Ext.Loader.setPath('Ext.ux', 'ux');
Ext.require([
'Ext.layout.*',
'Ext.ux.*',
'Ext.grid.*',
'APP.controller.Controller',
'APP.view.MapPanel',
'APP.view.FilterPanel',
'APP.view.Viewport'
]);
var start_app = function() {
var app = Ext.application({
name: 'APP',
appFolder: 'app',
requires: [
],
autoCreateViewport: true,
uses: [
'APP.controller.Controller',
'APP.view.MapPanel',
'APP.view.FilterPanel',
'APP.view.Viewport'
],
launch: function() {
},
controllers: [
'APP.controller.Controller'
]
});
}

Answer 1

In the above code you only need controllers:['Controller']. In turn, in the controller file you need views:[], stores:[] and models:[] depending on what you want the controller to pull from the server.
Another example: Let's say you code a grid and it uses number column, so you need requires:['Ext.grid.column.Number' in the grid config.
What I do is that I put there minimum I think is required, and then I watch the console. Either I get an error and I fix it or I get "Synchronous Loading" warning that I also fix.
For more details see: http://www.sencha.com/blog/countdown-to-ext-js-4-dynamic-loading-and-new-class-system