Personally I'd consider the cost of the Xeon 8270 prohibitive; for the price of one of those CPUs (~£7k here) you could buy four 3970X's or two 3990X's, both of which are CPUs that'd spank the 8270's overpriced arse in most workloads. The only significant downsides are relatively few workstation-class boards and having to use relatively expensive EUDIMMs if you want ECC.
I have a 3950X myself (an absolute steal for the price) but if you need any heavy IO requirements it's not well suited; it sounds like you might use video capture cards in which case you'd need to calculate your lane usage and bandwidth requirements very carefully.
As excellent as they are, Optane is overkill for a boot drive. Only buy that if you've got money to burn, else I think you'd be better served by a good enterprise NVME drive. If it were me I'd go for something like the 1TB Intel P4511 which is in the same price ballpark as the 280GB 900P.
The Cyberlink one I don't know about, but Handbrake itself doesn't scale to more than 16 threads - and indeed if you're only working on encoding a single video at a time, efficiency and quality drops off the more threads you get the encoders to use. I've switched to using command-line ffmpeg pretty much entirely for my video workloads and whilst I can get it to use my 32 threads, it's difficult - sometimes one of the filters becomes a bottleneck (and this is where you still want high clocks) and the drop in quality isn't worth it for me (I'm not doing anything time-critical). If you haven't already done so you should start doing some performance monitoring on your current 2P setup to see what utilisation is like and where bottlenecks might lie.
