If is video is posted on YouTube, the sound of the video is processed during the upload to YouTube, Every video on YouTube has been processed by YouTube.
In addition to that fact, I think there are very many other variables between a demo and trying the Rigs at home.
If you like the sound of Rigs on a demo video, and the audio in the video was recorded direct from the Kemper (not a room microphone), and you listen to the the Rigs using the same speakers you used to listen to the demos, and you have the Kemper turned up enough to drive those same speakers at a similar volume, and you are using a similar guitar with similar pickups, and the pickups are adjusted to a similar distance from the strings, and you use the same volume knob technique as the player in the video, and you play with a similar enough right and left hand approach to the player in the video, then the Rigs should sound similar, other than the the post-processing done by YouTube.
I sound like me, no matter what the demo sounds like,