Hatti was the capital of the Hittites, a powerful civilisation that left us the usual sculpture, some fantastic cuneiform tablets including a manual on chariot training and the odd literary mention elsewhere. Biblical Uriah was a Hittite for example and you cannot have a battle of Kadesh without Hittites.
Scholars though seem to have struggled to identify any particular Hittite evidence as opposed to evidence of the peoples of Hatti. Some decided there were no Hittites in the sense that there were Mycenaeans or Sardana. It seems Hatti arose from the existing pre - Hittite peoples of the region and established its dominion over others. A home - grown imperium if you like. So that’s the Hittites unless scholarship has moved on.
My Hittite retinue for Mycenaean Lion Rampant is going to have two squadrons of chariots, one unit of foot sergeants for the regular troops and the rest as conscript bow or spear.
I’m interested to see how it copes with the Sea Peoples.