it's probably a better solution to resize 4K down to 1440p in a real time instead of long conversion with loosing HDR data
in All settings search for "resize", set frc.frame.resize = -25601440
in this mode my old Ryzen 1700 shows 144 fps with no dropped frames while pure 4K can only reach 120 fps
and I'm talking about MPC-HC + madVR + Aviysynth Filter + disable 10-bit output (!)
https://www.svp-team.com/wiki/Avisynth_Filter_(AVSF)
but don't push madVR settings too high, keep the GPU load at reasonable level...