Is Time Machine sufficient in the case of a reformat?

I installed OS X Server 4.0 on top of Yosemite and my VPN got hosed. I've tried many things to fix the issue including attempted uninstall of OS X Server. Now I am going to re-install the OS. In preparation for said install, I setup time machine for the first time.

Will time machine be able to restore files after a OS re-install or do I need to consider manually backing up files? Second, will time machine restore the potentially broken part of my OS as well (considering I ran time machine after the fact)?