I have a game running on a client's machine.
The game was overall smooth on Chrome but when it comes to NW.js it is a bit laggy.
Is there anything I could tweak for the NW.js version ?
Based on your description, I could only have assumed that you exported using older version of NW.js
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NW.js and Chrome use the same browser engine - Chromium - so I'd expect performance to be identical.
I am using the latest version to export (0.46)