The choice between Ryzen lower end CPUs and a 1900 should be driven by what you want to hook up to your CPU.
Ryzen R3, R5 and R7 CPUs support 24 PCIe Lanes direct to the CPU.
Let's break it out for best performance:
One 16x Video card, suitable for anything from basic desktop apps and displaying video (like an NVidia GT 1030) to playing at higher levels (with like a GTX 1070/1080/1080ti)
One high speed storage device for booting, active apps and the (why do we still need this?) virtual memory page file. (like a Samsung 960 Pro 512mb NVME M.2 PCIe x4 drive)
Only four directly linked PCIe lanes left. Decisions, decisions, what kind of additional service or feature would you, or I, want to operate at it's fullest potential and how many PCIe lanes does it need?
A high end audio card would be PCIe x1. Some SSD drives are configured as PCIe x2 cards, several hard drive and RAID controllers are available as PCIe x4 cards. Or, maybe a PCIe x4 multi-link NIC so your PC could host a LAN party with no external switch, router or hub.
Ryzen R3, R5 and R7 CPUs are adequate to support most needs.
Performance will improve as more code is updated to better utilize these AMD parts. Intel has "owned" PC computing long enough that it is understandable that AMD's new kids on the block cannot win every comparison right now.
Threadripper, any Threadripper, opens up new possibilities. ALL Threadrippers support 60 PCIe lanes!!!
Full PCIe x16 x2 SLI, or Crossfire, is fully supported. And there are still 24 PCIe lanes left, just like what the Ryzen R3, R5 and R7 CPUs started with.
Sorry, three way SLI and Crossfire are not supported. But ...
NVME RAID will be supported soon. Think two, or three, Samsung 960 Pro 512mb NVME M.2 PCIe x4 drives in one RAID striped array.
Storage warp drive (?), I don't know. It has not been done in public yet.
And we still have more available PCIe lanes going straight to the CPU.
Threadrippers are about high speed connectivity between the CPU and the peripherals that connect it to whatever you, the operator, are trying to do with your CPU.
The multi-core and multi-thread superiority thing is primary. But, IMO, being able to input and output CPU driven products faster cannot be ignored.
Its a little sad that code has to be optimized to take full advantage of Threadripper, and Ryzen's, full capabilities; but hey at least people are talking about doing it and the CPUs are robust enough to justify it.