ISO performance is down to the sensor itself, not the lenses. Also shutter speed & aperture on m43, FF or APS-C. f/2.8 @ 1/125 is f/2.8 @ 1/125 no matter what sensor is behind it.
The differences between the 3 sensor types are focal length, dynamic range & depth of field.
You could, of course, argue that an FF sensor has a better dynamic range, therefore you do not need to push the ISO as much as an m43 or APS-C camera in low light conditions as you can recover more when processing. But again that comes down to the performance of the sensor itself and it's ability to handle noise.
In terms of how much is out of focus, so the depth of field. That's quite difficult to put your finger onto definitively I think. As it varies so much between the lens being used, the camera it's on, and the circumstances it's being used under. However many will tell you through experience, shooting very wide open (so a low aperture number) on a FF camera can require your focusing to be bang on. You need to hit the eyeball as the bridge of the nose won't cut it, for example.
Sorry if that doesn't fully answer your question. Caffeine hasn't hit yet