You should btw. also set CPU clock governor to either acpi-cpufreq performance or intel_pstate performance, since governors like powersave, ondemand or schedutil can already cause severe stuttering at vsynctester.com, even without a compositor. The result should be 100% stutter free, at least that's the case for me with amdgpu.dc=0. This way you should be able to be absolutely sure if the result is badly affected by amdgpu.dc=1.