With the Intel 6850k or 6900k, Reaper will playback glitch-free right up to 100% CPU load.
With the 1800x (even with RAM running at 3200MHz), Reaper can not playback glitch-free with CPU load near 100%.
That said, when running the Reaper version of DAW Bench (using the 64Bit version of their Multi-Band Compressor for load), the 1800x outperformed the 6850k. (I've posted the figures here on the forums.)
When running the 32Bit version of their Multi-Band Compressor, the 6850k outperforms the 1800x.
With Ryzen, getting RAM to run at 3200MHz (and the motherboard to behave rock-solid) is a quest.
We've got an 1800x with RAM running at 3200MHz... and it's mostly flake free.
But... a pair of USB ports just stopped working.
X370 motherboards were rushed out the door. Worst launch I've seen in years.
I have no doubt the Ryzen platform will ultimately solidify... but for now, there's no way we'd build Ryzen for clients.
Threadripper certainly looks interesting (on paper).
We'll see how it goes in the real-world...