I can say that using temporal-sampling within materials does cause a bit of speckles for my use-case. No upsampling, just temporal-sampling to reduce texture-sample-counts in materials.
With the default, OOB Epic solution, there CAN be slight streaking/blending, and sometimes speckles, but these are slight. They ARE exaggerated with upsampling.
With DLSS 3.5, just turning it on, screen % 100, any streaking/speckles just-disappear (again for my use-case). I can even go down to a screen-percentage of ~40% before I even start to notice any graininess. An even 50% is eminently do-able…
VERY curious to see your results here. For what I am seeing it would be hard to improve on DLSS 3.5 but I’m curious…plz update!!