Could the latest VSfilter really fix it? Does that sound reasonably possible?
Absolutely, xy-vsfilter is much faster.
By the way, the error you had with trying to remove AC3Filter seems to be access denied, so were you running the CCCP Insurgent with elevated permissions as 'Administrator'?
It's possible to have issues in the future as all "1080p" videos are encoded differently. Some can require more CPU power to play than others.
If you have such issues, try enable LAV video decoder on the first page of the CCCP Settings application. After that, open the video in MPC-HC and confirm that it is being loaded by checking the Play-> Filters menu.