So far I'm pretty impressed with the high ISO performance on my EOS M6. Makes me not worry too much about auto ISO.I took these yesterday at Anheuser-Busch in St Louis. The high ISO shots are pretty usable without any noise clean up. Better with it but usable without it.
ISO 12800 without cleanup
ISO 12800 with +30 luminance noise reduction in Lightroom
ISO 12800 without cleanup
ISO 12800 with +25 luminance noise reduction in Lightroom