Get whatever kit your wallet can afford and you like the looks of .. CAS16 is better of course
2x16GB sticks is better than 4x8GB .. easier on your 5800x's IMC (integrated memory controller) and leaves you room to add another 2x16GB kit down the road if you want/need to
I ran 2x16GB 3200 CAS16 HyperX Predator's @ 3800 CAS18 1.392v .. I currently run 4x16GB Oloy brand RGB 3600 CAS18 sticks @ CAS16 1.380v
IF you run into stability issues with your new RAM .. some kits might require just a bit of a voltage bump to run XMP stable from it's default 1.35v .. so just up it to 1.36v .. 1.37v ..etc until stable .. IF it's your RAM that is causing stability issues
Make sure to update your BIOS first thing to latest greatest
Make sure to install the latest AM4 chipset drivers from AMD.com
Make sure you have a quality power supply to run everything that has more than enough wattage to handle transient power spikes from your system when under 100% load with an 80+ Gold or better rating from a quality manufacturer ... check hardware review sites before purchasing anything
I've ran the 5800x in my setup, in my daughters and it's now running in my wife's .. daughter runs the x570 Steel Legend (I ran it before her) and it's been a great solid performer.. wife runs the B550m Phantom Gaming 4 and it's been a good solid board too
I'd recommend getting a good air cooler over an AIO personally .. but that's up to you. I run the original Noctua NH-D15 .. daughter has the Deepcool AK620 .. and wife is running the be quiet! Dark Rock Slim on her 5800x
