this is the ram iam using, not tried for higher frequencies but i know people that have 3333mhz stable at cas14 and some people have achieved 3600mhz at cas16.
https://www.overclockers.co.uk/team-group-dark-pro-8pack-edition-16gb-2x8gb-ddr4-pc4-30900c18-3866mhz-dual-channel-kit-black-my-08r-tg.html
motherboard is this https://www.overclockers.co.uk/gigabyte-aorus-ga-ax370-gaming-5-amd-x370-socket-am4-ddr4-atx-motherboard-mb-554-gi.html