Settings Manager/Screensaver = xscreensaver-demo, a gui for xscreensaver
Is xfce4-power-manager just a gui for xset?
Is presentation mode the same as "xset s off -dpms"?
P.S. The solution to my problem was to issue "xset s off -dpms" and shut off the xdg-screensaver, as described in the README here. By itself, presentation mode did not prevent blanking. MX-17 full install, using Firefox to play movie.