To restart xfce panel (via cli/ terminal):
$ xfce4-panel -r

To Prevent Panel Use:
source:
https://unix.stackexchange.com/questions/38048/how-to-remove-all-the-panels-in-xfce

You can not delete all panels. The right way of doing this is to disable the panel from autostart.

Edit /etc/xdg/xfce4/xinitrc , find the line to start xfce4-panel ,
Comment the start line out by placing a ‘#’ in front of it change the line containing:

  • $panel  –to–
  • #$panel

that will prevent the panel from running .When you want to re-enable panel , just remove the # from that line.