How often does it eat the RAM. To be fair, looking at your webpack.mix file, it is doing a lot of work each time you make a change.
To clean some of that stuff up, i suggest combining files that aren't going to be updated/changed regularly (i.e: plugin files) once and then removing them from the webpack.mix file. That will generate one file.
Then all you need to focus on is the files you are going to change regularly.
Otherwise, every single time you make a change, you're re-compiling and re-combining files that haven't been changed which doesn't make sense.
Let me give you an example from the code you've provided:
All of this, is unnecessary. There's only one file that will be changed regularly and that's the frontend.js. The rest are plugins.