Tony Northrup compared the new Panasonic GH5 Low Light performance against the a7S, a7R II, GH4, E-M1 II, X-T2 & X-T20. And the result is that the GH5 beats them all:
GH5 at Amazon, BHphoto, Adorama and Panasonic US. In EU at Amazon.de, Cyberport.de and ParkCamera.