"Wasteunit" and things like that mean the unit has waste survival and waste-themed names, or whatever applies in that case. As for montags, at the end of each nation listing in the Advanced Description link, there's a list of montag units for that nation; upon recruitment, the template unit (whose gcost and rcost are averages of all the prices of units with that montag montag) will be permanently replaced with one of the units with that montag chosen at random. E.g.:
** Light Desert Bowman (Foulspawn), 7g, 11r, Bite, Axe, Composite Bow, Scale Mail Cuirass, Reinforced Leather Cap.
--- Has montag 1002, wasteunit and Ranged unit
** Light Desert Bowman (Foulspawn), 10g, 4r, Claw, Short Bow, Leather Hauberk, Leather Cap.
--- Has montag 1002, wasteunit and Ranged unit
** Desert Longbowman (Foulspawn), 9g, 7r, Weak Bite, Axe, Long Bow, Full Leather Armor.
--- Has montag 1002, wasteunit, swampunit and Ranged unit
** Desert Archer (Foulspawn), 8g, 22r, Claw, Light Crossbow, Plate Hauberk.
--- Has montag 1002, wasteunit and Ranged unit
** Heavy Desert Archer (Foulspawn), 13g, 21r, Tentacle, Web Spit, Plate Hauberk, Buckler.
--- Has montag 1002, wasteunit and Ranged unit
** Heavy Desert Bowman (Foulspawn), 15g, 3r, Kryss, Short Bow.
--- Has montag 1002, wasteunit and Ranged unit
** Light Desert Bowman (Foulspawn), 9g, 5r, Club, Weak Bite, Composite Bow, Leather Hauberk.
--- Has montag 1002, wasteunit and Ranged unit
** Desert Bowman (Foulspawn), 10g, 18r, Tentacle, Weak Bite, Composite Bow, Chain Mail Hauberk, Iron Cap.
--- Has montag 1002, wasteunit and Ranged unit