Xcode search by file or class name

To search a file/class ⌘ + ⇧ + O (Command + Shift + O)

To See the current opened file in Project Navigator ⌘ + ⇧ + J

To go to line number in a file use ⌘ + L

Note: This partially answers the question, to see all .xib you can search it in project navigator as mentioned by one of the answers. But I think these shortcuts are awesome!

Type your search keyword in the text field at the very bottom of the Project Navigator pane on the left.

In xcode on left pane at the bottom there is a search field, just type xib, it should list all xib files. Same with other type of searches as well.

Place your cursor in this "Filter" with a keyboard shortcut: ⌥ +⌘ + J , or by choosing from the File Menu Edit > Filter > Filter in Navigator

Edit:

You can even use wildcards. For e.g., *m*1.x* will filter SampleXib1.xib, It's also incase-sensitive.