If I read your log correctly, it seems you have all the HDR settings turned on. (Metadata passthrough, HDR switching…) These settings seem to cause serious frame dropping with Nvidia’s default power settings. Has also been written here => [HDR Metadata Passthrough] - Plex HTPC for Windows and how to change it! (all in the first post) - Maybe changing the GPUs power setting also resolves your issue. It fixed it for me and my RTX 3050. 
#Edit: Some (up to 10) dropped frames at the beginning of playback and with frame rate switching on are normal*
