Navigation Bar

The design guidelines for navigation bars should answer most of your questions.

https://developer.apple.com/ios/human-interface-guidelines/ui-bars/navigation-bars/

Customizing the bar

By default, the title of the navigation bar is a label, but we can actually override it with anything.

For example, to add a search bar to the navigation bar, we can do:

searchController = UISearchController()
navigationItem.titleView = searchController.searchBar