Just a funny historical note on the atl-atl being too powerful!
When (not in Civ, in real life) the Spanish attempted a landing and conquest of what is now Florida in ~1505, a tribe related to the Tupi and Caribs living there decided to resist and fight back. The Spanish landed, fired their matchlocks to frighten off the silly savages, and strutted about in their nice shiny breastplates. The Floridian natives then attacked with their atl-atls, and the 2 surviving Spanish officers wrote about how surprised they were that such a primitive weapon could hurl a stone-tipped dart straight through their armor. The surviving Spanish fled. 50 years later another Spanish expedition returned and established a colony in Floridia... guns may not have been > than the atl-atl, but smallpox was.
As far as I've found (I'm a historian and anthropologist), those Floridians were the only people still using that most ancient (and powerful) of weapon technologies in the Western Hemisphere, though it begs the question of why it didn't experience a revival very quickly.
As for the UUs and buildings...
General consensus is that native americans didn't have access to horses until the 17th C., so giving Apaches horse-based uniques might not be very accurate. Unless you gave them a cavalry-era horse unit.
I'd suggest Toqui for Mapuchan UU, some sort of axeman modification. As for a UB I couldn't say.