Just before Christmas I got 2x 2920X, they weren't that great if I really thought about it, see here
TR2 is Zen+ and compared with my Zen+ AM4 CPUs the IMCs were not great on ones I had. I had 3x 2700X, one reached max 3466MHz on 2x8GB, another 3533MHz and last one I had was 3600MHz. 4x8GB I'd lose significant MHz, ~3333MHz which would be like say 4x16GB on TR2. The Zen+ AM4 CPUs were used on a daisy chain topology.
Also ZE/ZEA use T topology, AFAIK AMD FW is more tuned towards daisy chain topology, AFAIK AMD don't allow vendors to tweak FW like Intel, see this post
If you don't need the PCI-E lanes of X399 and don't wanna go TR3+TRX40, I'd say your better off going AM4. A R9 3900X does very well against a 2950X and has better RAM MHz/density support, due to the IO die you don't have latency penalty like in UMA mode on TR1/2. You also have option of 3950X, plus AM4 may see Zen3 and AM4 as mainstream gains more UEFI updates than the halo line up.