I don't own an RX-100 but I have been looking at some sample RAW files and the Camera Profiles that people here have made. I do own a Passport ColorChecker and make profiles for my Canon S-100 camera. Some comments:
If you are using a G-M color target and DNG Profile Editor to make profiles, you may be able to download the ColorChecker Passport software and use that as well, even if you don't have a Passport.
I am very happy with the color rendition I get with the ColorChecker software. However it doesn't seem to do anything at all for tonality. In my camera, there is no tone curve included in the created profile.
A free program called dcpTool is great for mixing, matching, and generally tweaking camera profiles. It is not easy to use, but worth the time it takes to learn.http://dcptool.sourceforge.net/Introduction.html
I use it to copy the tone curves from the Camera Standard and other profiles into my Passport CC profiles. It can be used for "cross processing" and other purposes as well.