You are getting involved with a complex subject. Virtually all localities start with the the nationally recognized codes [BOCA, IPC, UPC, NEC,etc] then modify those to some degree. In general; plans producers design to those codes; then the local contractor modifies as needed to meet local code. It's OK if they exceed local code. Usually the Plans Examiner will be looking for structural, electric and plumbing features that meet local building code. For example, local code may require 2x4 roof trusses on 24" centers in your area [lets's say Florida]. The plans may specify 2x6 on 16" in centers which would be good for northern Michigan snow loads. The plans examiner will allow that but also will allow the contractor to downsize to 2x4 on 24 which meets local code and reduces the cost of the house.