A couple of things:
1) 60fps vs 30fps is *MUCH* more important than 8bit vs 12bit. madVR has very high quality dithering, which means 8bit is not a problem at all.
2) You still seem to have 10bit output activated. Try disabling that if you know for sure that your display doesn't support 10bit at 4Kp60, anyway. It might not help with the stuttering/drops, but it should be better for image quality.
3) It seems you switched to 59.940Hz, while the movie seems to be 60.000fps. Try to get 60.000Hz instead. In Windows, it's the difference between "59p" and "60p".
4) The queues are weird. The decoder queue is 10-16/16, which means sometimes the decoder queue drops down to 10/16, sometimes it fills up to 16/16. It should really be 15-16/16 or 16/16 all the time. What kind of content are you playing? Which codec? Which decoder are you using? Software or hardware decoding?
5) The upload queue is in trouble, I'm not sure why. Because of that all other queues after that are in trouble, too, which is probably causing the frame drops.
You could try disabling automatic fullscreen exclusive mode in the madVR settings. Maybe that works around the issues, for some reason?