I just don't see a lot of room for improvement for AMD's APUs on the desktop. I think it was D8auer that produced the youtube video that demonstrated a whole slew of overclocking results for a 2400G with different memory sticks at different timings. When pushed from 1500 to 1600 Mhz, he saw very little performance increase. When pushing the RAM past 3200 to 3400 and trying to tighten the timings, he was also seeing very little improvement. For the APU in Renoir to exceed the TFlops in Vega 11 at 1.6Ghz, it needs to be North of 2.0Ghz. So, even if we manage to see the desktop APUs pushing DDR4 at 4266 on two channels, at just 2.1Ghz, its only really addressing the VRAM bandwidth starvation problem by roughly 30% over VEGA 11 with 3200 DDR4 and not making any significant gains on actual iGPU core video computation throughput.
I'm going to be quite shocked if desktop Renoir exceeds Picasso performance by more than 20% when the performance limit is entirely iGPU related. On titles that are CPU starved, or that were hitting thermal/power walls on Picasso, Renoir should show significant improvements.