I plan to revisit the docs for Ray Tracing over time and expand upon it. With the state that the features are currently Early Access, we don’t always “fully” document as much as we would for a Production-Ready feature that is finished.
I’ll consider adding command list information, but no promises at this time. Again, denoisers shouldn’t really be tweaked by designers or artists just making adjustments to the scene.
So some additional info about denoisers (and as a side note, I’ll consider adding this type of description in the near-term future over command lists that users don’t really need to adjust):
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Each feature ray tracing feature has a denoiser available.
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All this denoiser does is take the low sample count (a single sample per pixel) which looks like a lot of dotted points in the case of shadows, GI, and so on. The denoiser takes that low sample count and does some magic to soften, smooth out the result, and make it possible to use during real-time. While there is some minor quality loss because of using a single sample vs many hundreds or thousands per pixel (like offline renderers), however, the results are still fairly accurate to that of an offline render except in real-time.
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Because each RT feature is different and self-contained, a denoiser for ambient occlusion or GI isn’t going to work the same as one for shadows. So they have their own for each feature. Then for each Denoiser, the additional commands you see are used by programmers to write their denoising algorithms.
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Denoisers support up to 4 samples per pixel.
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This simply means that on a light casting a shadow, I can increase the SPP between 1 and 4 and the denoiser will smooth and soften the results as needed to match an offline render. When you use something outside of this range, it should fall back to just using however many samples per pixel you punch in without the denoiser (so you see a bunch of dancing points on screen for that ray traced feature.)
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Using a value of 0 doesn’t disable the Denoiser, it just says no samples for that feature. In the case of a light’s shadow, if you punch in 0, there are no samples being used so everything is dark because the light isn’t being ray traced.
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As for all the commands, I’m still on the side of the fence that we’ve exposed the important ones to the lights and post process volumes that matter for artists and designers to make adjustments. Beyond that, I wouldn’t touch them at all.
Auto-Exposure
There’s an Option in the Post Process Volume details panel to set it to **Infinite Extent (Unbound). **This will do the same as scaling the PPV infinitely large without having to do that. You can just keep it the small box and tuck it away somewhere.
Feel free to shoot me a message or tag me. I’ll offer some suggestions and help when and where I can. 
Tim