My suggestion is to use nvm to manage node installations in userspace instead of using the system-provided nodejs (which is basically there because some packages need it as a dependency).
In this way you'll have whatever you'll need (and then some, like multiple node versions with separate versions of globally installed packages, something that you simply cannot do with a single, system-wide nodejs install....) and everything will be right in terms of permissions.
By the way, using an OSX guide to manage something under Solus is not an especially wise move.....
