The Legacy Voices ARE Panel Voices. Yamaha just moves Voices from previous models to the legacy folder so when we select from the Voice Category buttons, we will see mostly new Voices for that model.
The XG/GM folder contains Voices WITHOUT a Voice Set File. If we select an XG or GM2 Voice and open Voice Set we can create the equivalent of a Panel Voice and save it as a User Voice. Then when we select the User version of an XG or GM2 Voice it will have DSP effects and/or Arpeggiator/Harmony settings, Mod Wheel, Pitch Bend, Filter settings, octave range for R1/R2/Left etc, assigned to it just like the Panel Voices do.
Joe H