Imaging Resource and DPReview have updated their comparison tools to include the Panasonic GH5 and Olympus OM-D EM1 Mark II. The Olympus seems to be a hair ahead of the GH5 in ISO performance, but you can check out the tool yourself. The Image Resource Comparometer can be found here and the DPReview studio scene can be found here.
Panasonic GH5 B&H Photo / Amazon / Adorama
Olympus OM-D E-M1 Mark II Amazon / B&H Photo / Adorama