I recently built a computer with a 2990wx Threadripper 2 and did a quick test to test the cpu render time. This frame renders in 1 min in Arnold at 1920x1080. (Please ignore the odd distortion on the window)
I’m using stock settings clocked at about 3.2 ghz per thread at render time. With a proper motherboard and water cooler you can overclock to 4 ghz per thread which is pretty amazing with the 64 threads. I highly recommend the 2990wx.