This small tip was shared by Jenny, (40th) at Asgvis.com long time ago, but still very applicable.
Set the QMC Sampler Adaptive.A @0.85, and Noise sampler @0.005. I've made a test scene with a emissive material.
Surfaces Material : default fresnel reflection, highlight glossiness = 0.8, Reflection glossiness = 0.8, subdivs = 22 *settings are written on the bottom of each image.
This render shows many splotches
Light Cash samples @1000 smoothed a bit the splotches but not enough.
QMC Sampler Adaptive.A and Noise sampler changed. No Splotches.