If you need to support IE11 I recommend SCSS, using node-sass to avoid adding Ruby to an otherwise nodejs stack.
If you don't need to support IE11, consider just using native CSS; making use of custom props (variables) and calc. Those two features give you what I feel are the most valuable aspects of a preprocessor anyway. Preprocessor nesting tends to encourage unnecessarily long selectors.
Either way, use a post-processor (eg. postcss) to add in property prefixes; don't use mixins. It keeps your original code cleaner and you don't have to keep track of which props still need prefixes - ie. you have to know when you add them because you have to know if your site works, but with a post-processor you don't have to keep track of when to _remove _them.