There is two default UI elements in my emacs config:
Line numbers on the left and two lines at the bottom. One for the status bar and one for the "mini buffer" (where you put commands, search text, and receive short messages). Everything else is just the buffer (file) I am editing. You could turn the line numbers off with a simple configuration and key binding if you wanted, along with all the other UI elements.
This goes to the "Zen" of my emacs config. Its always just the buffer I am editing unless I need another dialog or UI element. The trick to making this work with no tree based folder explorers are Projectile and Helm. Projectile adds "project" concept to emacs and Helm adds fuzzy searching of everything almost everywhere that matters. Both can be taught to work around git repos. So you can say, whack some keys and see a list of files in your project. Then start fuzzy matching in the helm buffer that results by typing say three letters of a file. If its unique you press enter. File is open. If I really need a tree or explore a directory there is `dired` mode which lets you walk around the file system. There are even tree modes that I find pointless after using helm and projectile.
There is nothing built in by default. That is the biggest problem with emacs. You don't just sit down at it one day and get a polished environment that fits with what you like. It is something that is worked at. You eventually learn at least a little elisp and your customization powers keep growing. Eventually you either quit emacs or are good enough at lisp and configuring it that it becomes obvious, if not trivial, to do most things other editors can do.
Generally speaking it is almost certain you can customize it if you are asking a question like, "Can I do X.". Everything in emacs, even configuration dialogs are just text buffers. You just teach emacs how to interpret different text buffers in different ways to implement special functionality. Most of the heavy lifting of integration with most languages is already done if your language is remotely popular.
This was a long answer, but that goes to the heart of emacs. If you want a zen mode, emacs is there for you. You want a mode with weird little widgets and build output things everywhere, emacs has your back. :)