Interesting. I have a Ryzen 1700 as well with a persistent OC of 4GHz that does up to 600 h/s with the current XMR algo with no issues whatsoever but only getting 670 h/s on randomwow. From what I've gathered, this should be doing around 4 kh/s.
Someone else was having issues with overclock. Have you tried stock speeds?
I will as soon as I get the chance. Would that be stock as in default 3.0 GHz with 3.7 GHz Turbo or set it up at a persistent 3.0GHz explicitly?
I dunno. The best place to ask is probably #monero-pow channel in freenode. I haven't had any issues running with Intel, and I've heard that ryzen should be even better. So I'd expect you should get at least 3-4x your CN hashrate.
I have a box with a very old Intel chip that is OC'd but it properly scales up from its XMR hash rate to a factor of 5.5x with randomwow. Apparently, it has no issue with an OC'd Intel chip. Incidentally, I have an older FX 8120 that is also OC'd to 4GHz that does around 270 h/s with XMR but only 360 h/s with randomwow; failed to scale up to the expected hash rate just like my OC'd Ryzen 1700. I still haven't gotten the chance to try it with stock clocks as you suggested but hopefully soon and will report then.