Decent RAM is a big deal with Ryzen. This review will help a little.
Ryzen 3000 Memory Benchmark & Best RAM for Ryzen (fClock, uClock, & mClock)
The main issue with RAM overclocking is that there is a performance hit due to not running the mclock (memory clock), uclock (memory controller clock), and fclock (infinity fabric clock)at 1:1:1 ratio.
With memory speeds greater than 3600MHz (mclock > 1800MHz), fclock caps at 1800MHz and uclock switches to a 1:2 ratio with mclock. Enabling 2:1 mode crosses clock domain boundaries, imparting a DRAM latency penalty of approximately 9ns that may be overcome with additional memory clocks, higher CPU frequencies, or sub-timing adjustments.” In other words, 2:1 mode hurts performance, but not so badly that it can’t be made up for elsewhere.
You can still set a fclock frequency above 1800MHz, but there is a hard wall at 1917MHz. This is why everyone is an IF1900 and using 3800 RAM maximum. They are trying to avoid the latency penalty of running outside of 1:1 and IF is at maximum no more than 1900. This then limits RAM frequency to 1900 as well or DDR4 3800.
The most performance will come from tightening RAM timings of good samsung b-die RAM. If you are luckly samsung b-die kits at CL16 3600, can be overclocked to DDR4 3800 RAM and have timings tightened to CL14 at 1.5Volts. This is why a normal overclocker will target DDR4 3600 CL16. If you can't get IF1900 stable you can at least try for IF1800 and DDR4 3600.
DDR4 3800 CL14 kit, very expensive but good for a normal overclocker who does not have a lot of time to tweak or research.
An enthusiast will bin for the best CPU and RAM possible. Then sell the dross on ebay or in the systems they build for customers.
4174MHz 12-12-12-28-1T on 2x8GB Patriot Viper Steel 4400C19 this is at 2 volts for the DRAM. If you were to do the same at DDR4 3800 with 2 volts DRAM. Then over 12k time spy cpu is possible (all core 4.4-4.5GHz). Don't put 2 volts into b-die 24/7.
Gigabyte Ryzen RAM overclocking
RAM overclocking: 2x8GB Patriot Viper Steel 3866 CL18 (Hynix ICs) on MSI X570 Godlike with 3700X
RAM OC results: Patriot Viper Steel 3866 CL18 on Asrock X570 Taichi with 3700X