Depends on your mobo (MEG / Aorus / Zenith ?? ) , i would check ram kits which were tested and approved by manufacturer.
Regarding speed and timings, if you are planning to run it stock, get 2933/cl14. Thats the best you can get. If you are on budget, go with C15-C16 but not higher.
Depends on the price drop on 2990wx, new 24core might be amazing choice. Just wait for benchmarks. New platform supports 3200mhz as well and you can upgrade later to more powerful CPU. But that means you need to pay for better, more expensive mobo.