I played a bit with power_profile settings and it turns our that whenever profile is set to high, mid, sound stuttering is pronounced. Yet, once set to low, stuttering is gone (or unnoticeable).
If anyone wants to try (adjust path to suit your hardware):
echo low > /sys/class/drm/card0/device/power_profile
Then the actual frequency can be verified by:
Also dynpm power_method does not really work, there was another bug report recenty that the frequency is never lowered if dynpm is used.
Additionally, given the recent fuss about pcie_aspm=force (and possible effect on PCIe), sound stuttering is present regardless of the setting.