How much smaller is the RP to the R?

Going by the images, we added the R into the images and scaled them up so that they are approximately correct.

This is the approximate size of the RP compared to the R.  As you can tell, the grip remains quite good, slightly smaller than the EOS R, but the body is certainly shortened.  The EVF sticks out less and makes the RP more compact. Looking at the top view, you can certainly see it's a much more simpler ergonomic model, similar to that of the M50, or the lower end Rebels.

Overall the RP may make a nice second camera body, or a travel camera, it's certainly smaller than the EOS R.