With document libraries, there isn't a permission level to restrict deletion of document libraries. There is the standard out of the box 'Manage Lists' permission that includes the ability to create or delete lists/libraries.
Lots of exciting announcements from the SharePoint 2018 conference in Las Vagas, but one area I started to play with is the newest sp-starter-kit project from PnP.
Learn to use the latest list formatting capabilities and apply them to existing sites with PnP PowerShell
With SPFX, you will notice you get a lot of extra files for configuration, libraries, temp code and compiled code; a lot of clutter and noise that's not needed as part of the majority of development, it just gets in the way when I want to focus on the code!
At the European SharePoint Conference 2017 in the Hackathon results session, Waldek Mastykarz from the PnP team announced the Office365 CLI which gives you the ability to manage an Office 365 on any platform. I had the idea to run this inside the Azure Shell
One of many cool announcements from Microsoft Ignite 2017, was the introduction of SharePoint Modern Themes.