So I've found that with DirectShow enabled, my DeoVR player will start video lagging behind when using any other hardware decoder other than the old CUVID NVidia option. I also have a lot of frame dropping and no overhead when playing higher resolution videos, anything above 6K. My rig uses an Ryzen 5 3600 CPU with a GeForce RTX 2070 Super videocard, using a Quest 2 VR headset with Oculus Link, so I should be able to support higher rez videos with no issue.
When I turn off DirectShow in DeoVR, I'm able to use a better hardware decoder like D3D11 without any video lag, and I'm able to play 8K videos with few frames dropped and some remaining overhead, so it's way more stable. However, I get two different oddities happening depending on my other settings:
If I have the Unity player turned on instead, the sound will sometimes ignore my PC audio settings and exclusively use the audio output from my Quest 2. This differs from the default setup where my audio comes from whatever audio device my PC is using, so I usually use the nicer headphones that I have connected to my PC.
If I turn off both DirectShow and Unity, some videos refuse to start playing. If I however then turn on DirectShow or "use alternate player", the video will start playing, and I then turn those settings off again, the video will continue to play, so it seems the video needs to jump-started somehow.