They run in one of two channels.. One is at the TOP of the wall (HEader ovre what appears to be a slide out) outer is in the footer.
If you cut more than 4 inches from the floor.. Odds are good you will miss everything.
Problem is they are odds.. At some point the wires need to come up or down.. If there is any way to access the area ou are going to cut into before you cut.. Do so.
You said the cabinet under the TV... Odds are there is nothing there IF wires run UP thy will hug (or be in) the side walls of the cabinet, not the middle of the back wall.