Ok, so you have a slow telephoto on your new EM1 mk2 and feel a need to shoot at 1/1500th indoors in poor light. Not a realistic scenario probably, but what the heck.
ISO 25600, no processing applied other than Lightroom default settings.
Good impression of detail, but obvious Olympus “film grain” noise.
Processed for a pleasing balance of smoothness and detail. Colour has gone off a bit.
The crop of above showing a loss of implied detail in favour of visual cleanness.
This is an unprocessed ISO 6400 image. It shows much the same detail and noise, but the colour is more accurate. Up to 12800 the colour stayed pretty true, but at 25600 it went into cold hues.
The truer colour