Threadripper's architecture loves high frequency RAM, though it can be a bit picky at times and you will have a far better experience sticking with vaildated RAM … though you certainly don't have to.

G.Skill have just announced a 32GB kit of four DDR4-3466 modules, with timings of 18-22-22-42 and plenty of RGBs.  On the Threadripper 2950X system they used as an example, the DIMMs were perfectly happy running at the default of 1.3V.   They will be available relatively soon and you will be able to spot them thanks to the TZRX branding they will sport.