I wanted to give a try to SVP. My gpu is powerful, 6900 XT, so i install it and setup the hardware acceleration with rocm. I get 4k60 fps with svp to work fine. I tried 120 fps, as i own a lg cx that can handle it, but i couldn't get at constant frame-rate.
I am using kodi to access my collection, and use mpv as external player. Something is strange, if i start mpv and svp with a command line in a terminal, in my case "mpv --input-ipc-server=/tmp/mpvsocket --screen=1 --fs=yes FILE", it is working fine. -screen=1 is my lg cx as you figured.

But if i start mpv using kodi, i get the svp OSD, same as before, but it quickly became extremely laggy after a few seconds, just after the svp osd disapear.

My playercorefactory.xml say kodi should start mpv with exactly the same option as my command line in a term, so i really don't understand what is happening.

My playercorefactory.xml :

<playercorefactory>
  <players>
    <player name="MPV" type="ExternalPlayer" audio="false" video="true">
      <filename>/usr/bin/mpv</filename>
      <args>--input-ipc-server=/tmp/mpvsocket --screen=1 --fs=yes --log-file=/home/satan/mpv-log.txt "{1}"</args>
      <hidexbmc>true</hidexbmc>
    </player>
  </players>
  <rules action="prepend">
    <rule video="true" player="MPV"/>
  </rules>
</playercorefactory> 

I also attach a log of mpv/svp when started by kodi.