Can I copy a Sass folder from node_modules and edit it?

I've been looking around at the node-modules folder and I found out that I actually have the bootstrap Sass files on there.

Can I setup mix to copy that to my resources folder so I can edit the Sass file in /resources, and compile it?

If I have npm run watch, will it work? I imagine calling npm run dev will always try to make a fresh copy of the bootstrap folder to /resources everytime the webpack is opened.