Does this apply to townhomes, duplexes, ADUs, modular and manufactured homes?

The model code provision covers one- and two-family dwellings and townhouses, so townhomes and duplexes are in. Modular homes are built to the residential code and are in. Manufactured homes built to the federal HUD code are governed by federal standards that preempt local construction requirements, so a local sprinkler provision does not reach them. Accessory dwelling units depend on how the jurisdiction classifies them.