A large part of differences between towns is pure corruption! Material strength is physical facts. Water runs down hill. Many other such things. Many towns are in one of a couple national form based codes plans where if you follow the rules as laid out there is no need for approval as the engineering was already done for any generic house. If your town/state is not, or is but provides extras on top it is corruption: either the industry is trying to create a local monopoly via legal means; or your town board is trying to increase their power. Either way it is only making housing more expensive without serving any public good.
Not all houses need to meet the form based codes. If you want to do something different then you need a professional engineer to stamp and approve the plans - once stamped the town needs no more input.
Apartments and commercial buildings start to get more complex (but even then many meet form based codes as it is cheaper than calculating out all the stresses). However again professional engineer needs to approve the plans not the town.