2 Hour Dungeon Crawl is just that, a group of adventurers exploring a dungeon. You can use dungeon tiles or pen and paper to create the dungeon. Whenever there is combat, it is played on a battle board.
Warrior Heroes – Legends is a RPG type of game with minimal bookkeeping featuring various encounters (including a dungeon crawl of its own). It has newer mechanics than Warrior Heroes – Armies & Adventures which include the In Sight mechanics & smoother combat system. It is also set in a different part of Talomir, THW's fantasy world.
Warrior Heroes – Armies & Adventures is an earlier set that includes rules for RPG adventures, another set of dungeon crawl rules, & rules for massed combat between armies.
While all THW rules use a reaction based system, the system is slightly different in the various rule sets. 2 Hour Dungeon Crawl perhaps has the simplest system, but that is primarily due to nature of exploring dungeons. Warrior Heroes – Armies & Adventures has the largest reaction system containing more tests and an addition character stat.
The lack of mass combat rules in Warrior Heroes – Legends can be found in Warrior Heroes – Warbands which accommodates armies the size of your typical Warhammer or Dragon Rampant game.
For really large battles, there is a fantasy set called Rally Round the King, which is element based like HoTT or Fantasy Rules.
Rounding out THW's fantasy rules is Red Sand Black Moon, a gladiatorial combat game.
Hope this helps.