[ashlar]

I changed the settings to DXVA2 copy back last night and immediately everything improved and is basically smooth. This is odd as reading the notes suggested this mode would be slower.
The vRAM is still peaking at 1936Mb. I suspect it would use more than 2Gb if I had more.

I suppose you could lower vRAM requirements by lowering the GPU queue size. Maybe you won't need it, since you say everything is smooth now, but keep it in mind.