Thought I'd post an update. Last week I received the new XX1 chainring and r/d. Installed them and my grinding issue disappeared, (duh). The chainring had some odd, not obvious wear. The new chain and chainring did the trick.
As for the creaking in the r/d, well it's still there. Even the new r/d makes some noise. After changing gears, up or down one gear, I get a creak after one or two revolutions of the cranks. Really to have two r/d do the same thing.
Today I removed the cassette, checked the free hub, re-greased, and reassembled. I inspected the assette and free hub spline, both looked like the day I installed them. The cassette has about 700 miles on it, and it looks like my other cassette with 200 miles on it.
I made a b-screw adjustment (to set the jockey wheel at 12mm from the 42T cog as the user guide indicates). After doing that bit of maintenance and adjustments, nothing changed, still a small creak (sometimes) after shifting gears when out on the trail. Note, my FS IP-036 does not do this, however, I'm on my second r/d on that bike as well. A week after building the FS Chiner, I exchanged the r/d because it was creaking all the time, not just intermittently. However, the replacement r/d for that bike now has about 300 miles on it and it's been fine.
It's not like there is probably anything seriously wrong, just slightly annoying to have the drivetrain not be perfectly smooth and quiet. I may bring the r/d back to the LBS and call SRAM one more time to see if they have any suggestions.