Keep in mind that most 3600MHz CL16 and CL18 kits are sourced from the same pool of E-Die (a rating of it's quality) memory modules from Samsung. There's a very, very high chance that the CL18 kit can be tweaked to CL16 timings and it will be perfectly stable.
The latency does impact performance for memory intensive applications, but it's not an impactful difference on machine learning or computational workloads. See more here:
Seeking answers? Join the AnandTech community: where nearly half-a-million members share solutions and discuss the latest tech.
www.anandtech.com
When we reviewed Ryzen's latest iteration we briefly checked out different DDR4 memory speeds but now that things have settled we were put on a mission to...
www.techspot.com
stub Memory speed on Ryzen has always been a hot subject, with AMD’s 1000 and 2000 series CPUs responding favorably to fast memory while at the same time having difficulty getting past 3200MHz in Gen1. The new Ryzen 3000 chips officially support memory speeds up to 3200MHz and can reliably run...
www.gamersnexus.net
Memory tuning is a deep rabbit hole that I don't advise anyone but overclockers and record-breakers delve into. Otherwise you're going to be ironing out things for a long time. XMP profiles for the 3600MHz CL18 kit will be more than fine.
Your motherboard choice and luck factors highly into whether picking faster memory actually benefits you.
If you can wait, Ampere cards will be faster for machine learning purposes because NVIDIA is building up the Tensor core logic in Ampere to accelerate those workloads (which means machine learning in general is still dependent on CUDA workflows for the forseeable future). This is partly why RAM isn't a big sticking point for the work you want to do - most of it is going to take place on the VRAM allocated to the GPU.
Ampere's launch is due for early September, with an initial release in mid-September. We might only get stock locally at the beginning of August, and it will be expensive. The Ryzen 4000 series is due for October, along with RDNA2 in late October or very early November in order to skip most of the buzz created by pre-orders opening up for next-gen consoles.
So, you could always wait for a Ryzen 4000 series chip and discounted RTX 2080 Super models. There will be performance improvements, but it's impossible to say how much that would be worth to you right now.
What some people are doing now over at /r/buildapc is buying their systems now with cheap APUs like the Athlon 3000G, and planning to swap it out for a Ryzen 4000 series chip when it becomes available. That way the rest of the system is built, it's just the processor that needs to be launched. Quite a good idea too since most boards will need to have their BIOS updated for the new chips.
EDIT: Not sure if the ASUS Prime B550-PLUS would boot with an Athlon 3000G though.
B550 is an X570 chipset with things chopped off to make up for the lower price, and to reduce thermals.
You get PCIe 4.0 support for the first and second slots (dividing in to PCIe 4.0 x8/x8) as well as a single four-lane PCIe 4.0 M.2 slot for an SSD. The second one is through the chipset at PCIe 3.0 x4 or x2 depending on the board vendor.
