I've updated the original post with the new approach to releases as I outlined in January. This means you can now download your own NW.js versions to use with Construct 3, allowing NW.js updates to happen without our involvement. It also means for the first time you can choose NW.js platforms other than Windows 64-bit, such as Windows 32-bit, Mac and Linux. Note however that no testing has been done with the editor the NW.js versions of Mac or Linux, so I can't guarantee how that will work. However NW.js has good cross-platform portability so in theory it should work the same as on Windows.
Hopefully this new approach works out smoothly; let me know if anything seems wrong.
Note NW.js 0.45.0 based on Chromium 81 came out this week, so to update to that version, use the new approach. New NW.js versions, including beta and patch releases, are announced on the NW.js blog and on their @nw_js Twitter account.