Why would you want a monoblock? Those perform worse than CPU blocks, and the VRMs don’t need active cooling on GB’s high end boards. You’re much better off with a proper CPU block, like a Watercool HeatKiller TR4-Pro (which works on X399 and the new gen, since the CPU mounts didn’t change).
I can tell you from personal experience, monoblocks suck, even supposedly ‘good’ ones. You’ll lose 5C (or more) in performance. Especially EK monoblocks, those are junk. They look pretty, but suck from a performance perspective.