The AM4 platform is still undergoing Bios micro-coding development atm and new Bios versions are being released addressing new DDR4 RAM as they come onto the market.
It's best to choose RAM kits that have been tested and listed on the the MB QVL. You will also have to update to the latest Bios revision. That way you have a better chance of compliance without having to Tweak your Timings and Voltages. Depending on the CPU will determine the OC you can achieve and the Ryzen "X" versions OC better.