Hmm, really funny because a I made a quick test, and doubling the noise thresold and haling the max rate (from 16 to 8 ), gave noisier result for … a longer rendertime.
An indeed, max rate back to 16 and pushing the noise to 1 do the trick ! I have a nice fog of noise in less than 5 minutes for a 4k, but I can tweak my light setup.
I really like the new “unification” of subdiv across material, light, brute force GI, etc. but with HDRI in direct light on a dome + IM in interior scenes, I have to uncouple the Dome and raise its subdiv to get acceptable noise, unless you have ugly undersampling on the border of the HDRI sharp shadows. And if I lower the global thresold, I almosty lose the speed benefit of working with IM