Here is some info on the Zen processors. It may not answer all your questions but hopefully it will get you started...
See the section on mobile processors.
As far as your laptop is concerned, you will need to choose from the options that HP provides.
HP designs and builds their systems using proprietary motherboards and system BIOS. So there is not a lot of flexibility when it comes to upgrades and replacement parts.
Sorry arcticwind, this did not help, tried myself and here is my practical result:
Ryzen 5 2500U does indeed support 2x16GB DDR4 2400 CL16 on HP Envy x360 15 machine.
Upgraded 2x4GB Samsung 2400MHz CL17 to 2x16GB Balistix Sport (Crucial) 2400MHz CL16 and it works perfectly! Active 2400MHz frequency, dual channel and CL16 verified with CPU-Z and AIDA64 benchmark.
Did not try 2666 RAM as did not have one and got super deal at Saturn.de (58% off) for Balistix 2400 CL16 RAM.
PS. need to update Wikipedia page for Ryzen CPU RAM support.
Super happy with AMD and HP. Cheers!
That's great, I'm glad it worked for you.
Sense the RAM plays such a big part in the operation of the new Ryzen processors, it would be interesting to me if you could post the before and after benchmark numbers for comparison.