A threadripper build would be overkill for rhino. you only really want a threadripper build if you need:
- lots of pci-e lanes
- huge amounts of memory
- your render engine only supports cpu rendering, not gpu
there are more scenarios of course but these obvious ones probably don’t reflect the needs of even the more demanding rhino users.
an am4 build with a 5950X would be a much better choice. the saved money (on the motherboard, ram, cpu) can be put into a higher end GPU. which will be a problem in the current situation anyway. an i9 from the latest rocket lake / 11th gen would also be very good, though this would draw noticeably more power in order to achieve the same single core performance, while still being way slower in multi threaded.
even with the currently highest end 5950X, there is still an upgrade path for the am4 platform, since amd will stack a layer of extra L3 cache on top of the die. already announced, expected to arrive by the end of this year. not sure though what performance impact this might have for rhino.
if you want to utilize any modern hardware well, you should just use rhino 7, not any of the previous versions. I don’t see any point in using the old versions.