There have been instances when Yarn borks everything up globally. If you haven’t hit it yet, then don’t worry about it until you do. Yarn puts globals into it’s own location, thereby excluding use of Node Versioning toolsets, like NVM. At work, we have 4.5.3, 5.0/5.1 and (upcoming) 6.0 versions of our product, each of versions are using different versions of Node and associated NPM packages, so I have to use NVM to manage all that.