I have a setup that some of you may find interesting...

I USE VAPOURSYNTH AND AVISYNTH AT THE SAME TIME

Using an NVIDIA GTX 1650 Mobile (no tensors)

GTX 1650 Mobile doing the processing
AMD integrated graphics HDMI output for display
10x interpolation (23.976 → 239.26 FPS)
1728×720 through AMD HDMI
Only 45% GTX 1650 usage

This is a hybrid GPU setup - NVIDIA doing the heavy interpolation work while AMD handles the display output through HDMI
Smooth AV1 decode with hardware acceleration

Yes the Nvidia is "trying" to do all the work but mostly failing but I see you are doing 10x Interpolation. But using the AMD for output means that once the Nvidia has finished it has to pass the result over to the Integrated GPU via the CPU which is the slowest transport possible.

BTW I might be missing something here, but what makes you think you are using AVI and VAPOURSYNTH at the same time?

I have a setup that some of you may find interesting...

I USE VAPOURSYNTH AND AVISYNTH AT THE SAME TIME

Using an NVIDIA GTX 1650 Mobile (no tensors)

GTX 1650 Mobile doing the processing
AMD integrated graphics HDMI output for display
10x interpolation (23.976 → 239.26 FPS)
1728×720 through AMD HDMI
Only 45% GTX 1650 usage

This is a hybrid GPU setup - NVIDIA doing the heavy interpolation work while AMD handles the display output through HDMI
Smooth AV1 decode with hardware acceleration

Can you share your generated script for this?

I USE VAPOURSYNTH AND AVISYNTH AT THE SAME TIME

Using an NVIDIA GTX 1650 Mobile (no tensors)

GTX 1650 Mobile doing the processing
AMD integrated graphics HDMI output for display
10x interpolation (23.976 → 239.26 FPS)
1728×720 through AMD HDMI
Only 45% GTX 1650 usage

This is a hybrid GPU setup - NVIDIA doing the heavy interpolation work while AMD handles the display output through HDMI
Smooth AV1 decode with hardware acceleration