[Warner306]

The trick of overwriting existing copies of LAV Filters is included the DSPlayer set up guide. It is also possible to use the external copies of LAV Filters installed in Windows if you use the filter rules provided at the end of the DSPlayer settings section.

For your remaining issues:

- Stuttering with RTX cards can usually be traced back to the video drivers. It is advised to download and run this utility. If that doesn't solve it, try one of the driver versions recommended in this thread:

https://forum.doom9.org/showthread.php?t=176013

- Slow mouse movement during video playback can be a consequence of playing movies at 24 Hz or is equally likely to be caused by overlaying Kodi's GUI over madVR's pre-rendered frame buffer. The frame buffer can cause menu navigation to be a little bit slower. Try reducing the number of frames presented in advance in both DSPlayer settings and the madVR control panel. This likely won't make navigation perfectly smooth, but it might improve it. Kodi is designed to be controlled by a remote, gamepad or tablet, so I wouldn't recommended using a mouse, anyways, because it is not meant to be used that way.

- Keep in mind, a small number of madVR settings are always controlled by DSPlayer, even if you configure madVR to be controlled externally. Check those few settings and ensure the madVR control panel matches. DSPlayer will always override the madVR control panel with its own settings. 

- The resolution shown in the madVR OSD should be taken as accurate. I don't know why the DSPlayer OSD would contradict this, but I would recommended ignoring the DSPlayer OSD and only using the madVR OSD in its place. There is far more technical information in the madVR OSD and it is always aware of its own output and will report accurate numbers. The DSPlayer OSD doesn't really provide any useful information, and I never use it.