People have been talking about "--single-process" but using "--in-process-gpu" has always worked for me, even with the Steam overlay problem. I've heard it doesn't work properly with Nvidia gpus but I've always tested on them and it always works..
I've been using --in-process-gpu since forever. It does not solve the Steam overlay problem. It helps it, on some systems. On mine, AMD GPUs, it works fine. On others with NV GPUs, it does not work. I've had many reports of this from players already so i know it's not fixed.
And it's actually related to NWjs spawning multiple nw.exe processes. For my system it's normally 3x nw.exe, for others, up to 5x.. and the Valve people that I and others have talked to about this, have said the Overlay injection (like on-screen-displays of MSI Afterburner etc) code doesn't do it correctly because it does not KNOW which nw.exe is the correct/game to inject.
This is also the same for some capture software, they do not know which is the game exe to monitor. However, OBS works 100% because you can select window capture and find the specific one, it's much more flexible.
This in the past can be fixed by using --single-process to force only one nw.exe on launch. But lately this is no longer functional, leading to crashes.
The NWjs team IS AWARE of this, as it was reported on their Github a week ago. Let's hope they fix it soon.
ps. There is no point getting aggro at Scirra. We all know C2 depends on 3rd party export options and that's an added complexity that can lead to issues. The issue gets fixed ASAP when we report it to these 3rd party options ASAP.