How tall can I make the houses?

As high as you want, provided you have ‘Main’ as the lowest part, and ‘Top’ as the highest part of your totem chain.

Why do some objects have LODs/Collision, while others don’t?

In some cases where the model should never be reached by a character, shouldn’t interact with it, or is simply too small, we felt it unnecessary to create collision. As for LODs, our cut off for not including LODs was “roughly” 500 tris. LODs are reduced 40-60% each level.