Ahhh, I found this in the Electron’s docs:
Note: This method is only supported on Windows 11 22H2 and up.
via: BrowserWindow | Electron
So, unfortunately, the acrylic effect is not supported on Windows 10.
I’ll update the option description.
Regarding the hidden X button, yeah it should not be there!
btw, what do you mean by Firefox?
I updated the login screen design in beta.3.