Something else that may be of note:

Setting amdgpu.dc to 0 sort of fixes the stutter and general performance issues
I'm seeing. Also there is no flickering/artifacts after a fresh boot, without
touching the performance level setting. It isn't 100% though, after some time
the desktop will start stuttering again when moving windows around. But right
after a fresh boot, or switching resolutions, it is completely smooth, as it
should be. In this mode however I notice the cursor skips frames. With
amdgpu.dc=1 the cursor never skips frames.

All in all, neither mode is usable for me and I've resorted to using HDMI on my
monitor which locks the refresh at 60 Hz.