I have two of those sticks paired with a 2600x and an Asus Prime X470-Pro.
Can't comment on how they are for Ryzen relative to the other B-die sticks available, but they seem to work reasonably well so far for me at least.
The largest detractor is that the only DOCP/XMP profile they provide is the 4000 cas 18 one, which isn't much use for Ryzen. Have not even tried it.
Without tweaking the timings yourself, you'll need to rely on your motherboards automatic settings for the frequency range you'll probably be aiming at.
These will probably be stable, but loose compared to what the sticks can manage, generally 20 or higher timings is what the prime pro defaults to at higher frequencies.
The Stilts Ryzen DRAM calculator can help to guide you to tighten the major timings. Many of the smaller ones are less important, so can be left on auto for the board to set itself.
The quality of the memory controller on the example of the processor you get is probably the largest limiting factor in respect to tight timings/high frequencies.
So far, trying to tighten the timings with a modest amount of testing using HCI, and an eye on AIDA reported memory latency:
Note, most of this was done with all cores on the processor at 4.2GHz at 1.3875V with the Vsoc at ~1.08V (1.1V Auto minus small offset).
Drop the core frequency a bit and tighter timings / higher frequencies may become easier to achieve.
C14 3200 HCI OK to ~100% at 1.375V, with manually set subtimings, not tried lower on the voltage yet at this speed.
C14 3266 HCI fail at 50% at 1.39V with automatic subtimings.
C14 3400 HCI fail around 35% on 1.4V with automatic subtimings.
C16 3400 HCI OK to 740% at 1.3V with automatic subtimings (this was with core set to XFR with automatic voltage and a 50mV negative offset).
C16 3466 HCI OK to 160% at 1.3V with a mix of manual and automatically set subtimings.
C16 3533 HCI fail at 50% at 1.35V with a mix of manual and automatically set subtimings.
C16 3600 HCI fail at 15% at 1.35V, with all auto subtimings.
C16 3600 HCI fail at 20% at 1.375V, with tighter manually set subtimings.
C20 3733 1.35-1.4V unstable and unreliable boot success (failed to POST on 1.4V).
C14 3200 and C16 3466 both give 63-64nS memory latency in AIDA. C16 3533/3600 gave 61nS, but not stable enough yet.
Its running at C16 3466 as a happy medium for the moment.
Only gripe about the system as a whole, is the latest BIOS update for the board (4011) which updates SMU engine (the Ryzen internal micro-controller than handles power control) to SMU 43.18.
Seems to change XFR (and possibly manual) power handling characteristics in a negative way from my persepective, as the all-core loaded XFR drops around 90MHz compared to the earlier BIOS and isn't so forgiving when using a large negative offset on the core voltage.
Perhaps AMD's internal modelling may have indicated it was necessary in respect to the products lifespan.
In practice, for me at least, effective core voltage is slightly higher, boost frequencies are slightly lower and stability is worse than BIOS 4008.
