First off, I would not buy more than 32 GB of RAM. Make sure that you split it among enough slots that you get to use all the supported memory channels, though.
As for the CPU, well ... I could never recommend i9-7980XE for Blue Iris. Not because it isn't capable, but because the CPU alone costs more than an entire BI server should cost brand new (SSD, big HDD, and Windows license included!).
i7-8700K is probably a little less capable, even with Quick Sync for hardware acceleration, but at 1/5th the price I think that can be forgiven. I'm pretty confident it would run your cameras just fine if you reduced frame rates to 15 FPS. And then with the reduced load you would probably be fine with 16 GB of RAM.
But since cost doesn't seem to matter for you, I imagine you're going to build another i9 system. In that case you'll need a graphics card. Geforce 1030 is a good option, and can be gotten with either HDMI 2.0 or Displayport to feed the 4K display of your choice. I have an opinion on 4K displays too. LG 43ud79-b is what I use and I love it.
As for the CPU, well ... I could never recommend i9-7980XE for Blue Iris. Not because it isn't capable, but because the CPU alone costs more than an entire BI server should cost brand new (SSD, big HDD, and Windows license included!).
i7-8700K is probably a little less capable, even with Quick Sync for hardware acceleration, but at 1/5th the price I think that can be forgiven. I'm pretty confident it would run your cameras just fine if you reduced frame rates to 15 FPS. And then with the reduced load you would probably be fine with 16 GB of RAM.
But since cost doesn't seem to matter for you, I imagine you're going to build another i9 system. In that case you'll need a graphics card. Geforce 1030 is a good option, and can be gotten with either HDMI 2.0 or Displayport to feed the 4K display of your choice. I have an opinion on 4K displays too. LG 43ud79-b is what I use and I love it.