I recently came back from a trip in Dolomites.
What can I say is that RX100 tends to badly underexpose in bright sun with snow all around, much more than newest DSLR and somewhat like old film bodies.
I often had to overexpose by at least a full stop in order to have a proper histogram.
Shooting Raw is not easy to understand what is still not clipped and what it is. I decided not to risk that much and keep some underexposures.
ISO 125 is not a problem. With RX100 you can shoot with quite small apertures without affecting the IQ that much, since the sensor is quite large.
1/2000th of a second at /5.6 and it's almost impossible to blow highlights, even with the whiter snow, fully lit by the sun.
With high contrast scenes, like deep into a forest with spots of lit snow here and there, it tends to overexpose a bit too much, so I had to lower the bias more than my DSLR.
Here ISO 125 is mandatory to try to get back some details in the shadow without starting a noise party.