Although xtype has been around since Ext 2.0, there is still a lot of confusion on what it is, how can it be used and what it is good for. The clarification in this article gives you all information you need to use xtype (and other [a-z]types) effectively.
Controller config option refs provides an easy way to get refereneces to views within the controller. However, there’s a catch. In some situations refs do not work as expected or cannot be used at all.