Which GPU do you have? A driver update may fix the problem (or sometimes a downgrade).
Make sure the "Hardware-accelerate video decoding" option is enabled in Options->Video. Check your CPU usage to see if MC is using software or HW acceleration.
Some things to try in Options->Video->JRVR settings:
- try the "Performance" preset (should be the default)
- enable the "Allow HW decoder direct rendering (...)"
- Press CTRL+J to enable statistics, see if there's something obviously wrong. There's also an option to log frame timings under Advanced options.
- Try other Scaling algorithms/options, start with Bilinear. Check your CPU usage to see if it's a bottleneck.
To answer your question - yes, you can use MadVR with MC. Just change the Video Mode in Options->Video to "Red October MadVR". Some new options to select the MadVR profile will show up. You can also use the "Custom" video mode to access the standard MadVR settings UI. MC ships with it's own copy of MadVR, so the settings are distinct from whatever MadVR settings you have on your other players.