wow...3x's for my name. Guess I better reply.
The resource page is Web AppBuilder Developer Edition - Customization Resource List it also has links to the install tips, etc.
From the official help Get started—Web AppBuilder for ArcGIS (Developer Edition) | ArcGIS for Developers
Robert Scheitlin, GISP or some of the others that have done a lot of customization might have a clue about what it requires, but my guess is any of the modern machines can handle it (I have used 4-yo Dell X10 tablet with no problems...win7). You WILL need an internet connection to ArcGIS Online ... OR a connection to your local Portal for ArcGIS. That isn't actually hardware, unless you consider network connectivity part of that.
There not a minimum hardware requirement that I am aware of. If your development machine can run JSNode then you should be good. I am unable to find an official NodeJS minimum system requirements page. But WABs help page lists the supported browsers: