Kent goes over this in excellent detail, but at this point my head was spinning. So, for those who come after me, I hope this helps them find steady footing.
Everything is linked.
Everything goes into its own collection: car -> car collection. traffic lights -> traffic light collection. bench -> bench collection, and so on. Assetize each Collection. These do not need a library override in the assembly file. They will work right out of the box!
The one exception is the parametric building. Generate one in the Asset File, and link that in as an object. In Assembly, override that one. Duplicate from there.
Enjoy Assembling your city! If you've made this far, you've earned it!
