Not sure I can completely answer your question but I too once had an R1, and I bought it because of the recommendation by Michael Reichmann on this site. I now shoot m4/3s, Olympus bodies (E-M1 and E-M5 M2) with a mix of Olympus and Panasonic lenses.
The phrase from his review that sold the R1, for me, was his comment that although the R1 at ISO 400 displayed noise when viewed on screen, it was irrelevant when printed. I have shot m4/3s at ISO 400 and 800 (and higher). The m4/3s sensor is slightly smaller than the R1's APS-C sensor. I have no back to back comparisons but have printed 8x10s and a few 11x14s with each and I don't feel as if I was giving anything away by using m4/3s. In my non-pro and non-scientific experience, some of the worry of small sensor noise disappears when you make prints. That noise you see on screen at 100% is often irrelevant and sometimes it's not even ugly when printed. I stopped worrying about this a long time ago, but I don't make large art prints for sale in galleries. OTOH, others do, and nowadays noise reduction software eliminates much of the "problem" at the cost of a few minutes editing.
For a while, I used the Panasonic 12-60/3.5-5.6, which is the focal length equivalent of the R1's lens (more or less) and I came to think of them as functionally equivalent, except the m4/3s system is a smaller and lighter (and you can change lenses). Online reviewers don't always have a high regard for that lens but Panasonic also sells a 12-60/2.8-4, which is regarded more highly. This is personal and anecdotal but I hope it helps.