Construct can export your project as a Windows desktop app using Microsoft Edge WebView2 . This is basically a copy of the Microsoft Edge browser engine that is...
could this replace NWjs for a Steam release? are there any performance differences?
Steam integration is not currently supported in WebView2, but it's possible it could be in future. For performance, as ever measurements are the way to test that, but I would not expect there to be any significant difference as both NW.js and WebView2 are based on the same Chromium browser engine.
sounds promising though!