I can confirm 495.46 spams /var/log/messages with the dbus-daemon messages and causes the kwin_x11 process to be pegged at 100% CPU, whereas 470.74 solves the problem (no messages and kwin_x11 behaves fine).
I’m on Slackware64-current (so no systemd here).
I did not try the “nvidia-fake-powerd” solution, as it’s easy enough to just revert to the 470 series driver.