If you are in need of some light reading before your Canon EOS R3 arrives you can now download the Advanced User Guide and Manual from Canons website. It’s 1037 pages of mercifully hyperlinked reading! Download HERE.
Although I am told delivery is still mid to late November in Australia for the EOS R3 there are now online noise tests for the EOS R3 over at the Digital Picture. The results appear more or less identical to the outstanding Canon EOS 1DX MK3 (although I will do my own testing when I take delivery in late November). Using the online comparison tool you can compare it to your camera of choice.