RP or M6 mk II

As a few others have said, it comes down to what lenses you get and like to use. The RP has a full frame sensor, but a fairly mediocre one by current standards. The M6II has the best crop sensor currently available. The noise advantage of full frame sensors, comparing equivalent generations is about 1 1/3 stops (the FF sensor has about 2 1/2 times the light gathering area of the crop sensor, which translates to about 1 1/3 stops). But in the case of the RP versus the M6II, the advantage is a bit under one stop, closer to 2/3. What this means is that, to get the full frame advantage with the RP over the M6II, you need to use lenses with similar apertures. If you compare the Sigma 56 F1.4 on the M6II against a full frame 85 F2 or F1.8, you won't see any advantage on the RP at all. But if you mount an 85 F1.4 or F1.2 on the RP, you'll get close to that extra stop (or a bit more in the case of the F1.2). With primes, you'll need big, heavy, and expensive to get the full frame advantage with the RP. And even to get equivalent performance, you're looking at bigger, heavier, and more expensive, just not by as much. As others have pointed out, it's with (some) zooms that you'll likely see an advantage with the RP, albeit at a size and cost. If you're the kind of shooter who likes to shoot a lot, or even mostly, with a zoom or two, the RF 24-105L will be great, and has no M equivalent. I had the original 24-105L for many years, and used it more than any other of my lenses until it finally broke. It was a fine lens, and from everything I've read, the RF version is better. Notice, though, that for pure quality of results, various primes on the M6II will actually give better results at a lot of the focal length settings of the RF zoom. But at the expense of convenience. In terms of performance, the M6II has it all over the RP. It's much faster. You can actually use it as a sports camera, with its 14fps burst speed. Even the lower speed of 7fps, which I use more often, is faster than the RP. In terms of AF performance, the RP is, at best, a match for the M6II, and according to some reports not even that.

The bottom line is that, if you like shooting with primes, and are prepared to spend a lot on the excellent, but bigger and heavier, RF lenses, you can see an advantage with the RP. Also, if you mostly like to shoot with an all-purpose zoom, you'll see an advantage, albeit at a size and weight cost (and actual cost), with the RP and RF 24-105. If you like primes, and would mostly be shooting with F2 or F1.8 full frame primes, you'll get equally good results with the various EF-M primes (most of which are F1.4), at a size, weight, and money saving.

From my perspective, I've realized that I would see no advantage at all to getting an RP, and considerable disadvantages. I've come to the financially painful conclusion that it's simply not worth it for me to get an R camera until I can afford the R5. I hope to do that at some point, because it looks like it's a simply amazing camera. I comfort myself right now with the consideration that I would just be frustrated to have such a camera with far fewer photographic opportunities, because of the pandemic. Most of my shooting is of other people, either in action settings (mostly runners) or informal portrait settings. Right now, I'm mostly avoiding other people, for obvious reasons.