FroKnowsPhoto has just compared the RAW files of new Canon EOS RP (B&H Photo/Adorama/Amazon) with Canon EOS R (B&H Photo/Amazon/Adorama) and Canon EOS 6D Mark II (Same sensor as EOS RP). You can see the dynamic range comparison in this video.
From the video, we can clearly see that EOS R has better dynamic range than EOS RP and EOS 6D Mark II, while dynamic range on EOS RP and EOS 6D Mark II are more or less the same. See the video above.
Canon EOS R Vs. Canon EOS RP: (Click for large size)
Canon EOS RP Vs. Canon EOS 6D Mark II: (Click for large size)