Question Is the X-Flare 3200MHz CAS14 RAM good for the 5900X?

3200 data rate, you have the guarantee that your memory will work with the XMP profile applied because Zen 3's maximum official memory data rate is 3200. If you get a kit like 3800 speed, it's a roll of the dice if you intend to use the XMP profile, your CPU may not be able to do it.