Again, I may be way off base here, but aside from the larger population areas (Knox County, Davidson County, etc.) and the 13 counties that did not opt out of the state's codes requirements, I don't think permits are required in any unincorporated area of Tennessee. Incorporated towns are a little different; there are 90+ that have codes requirements enforced through the state (in addition to the larger cities that do their own codes enforcement) but I didn't see any from Cocke County on the list I posted above.
You are correct. If the jurisdiction opted out then there is no permit required except the electrical. That is required throughout the state. The electrical inspector for our area only wants to inspect if you are adding circuits to the house.
One quirk in that law that allowed the opting out was that the jurisdiction had to opt out every year or they would be "opted" in. That may not be enforced though. I checked into all that as I was going to try and be the inspector for my county as a 2nd job but they opted out of course. I had to fill out a form showing our city had an inspection process and did not need the state. Also all places that do their own inspections will have to start doing plumbing and mechanical inspections if they do not do them now. This means that all inspectors will have to pass the certification exams for those two, to maintain operations. It is a mandate from the state because the international residential code (official state code) has the code sections for both of those disciplines included with it. The state really wants to enforce building codes throughout the state but doesnt have the political stones to mandate it for all those areas that opted out. The desire from them to have that requirement is because of the new energy code. If your jurisdiction adopts that code the cost of home construction will go up and you will be limited on the number of windows and exterior doors you can have plus you will not be able to use but very few incandescent bulbs in your fixtures. It will increase the amount of insulation required depending on your area. It has reinstated the old "FHA" requirement of insulating crawl space floors which is the biggest mess and waste of money I have seen. The majority of that, that was put in years ago was subsequently taken out by the homeowners because of the mess. Either that or you have to insulate the crawl space walls, leave out the foundation vents and put in air exchangers to try and keep mold from forming. That is the stupidest thing I have ever heard of code wise.
A story about the dangers of sealing a house up too tight. Guy was teaching a class I was at told of couple who sealed up a house really tight in an attempt to make it really energy efficient. A worthy endeavor you would think especially in this day and age. Well they did and after they moved in the kids pets started dying. (gerbils) They bought some more, they died too. Come to find out they had sealed it up so well that the oxygen levels were dropping the house and of course the gerbils were like the canaries in coal mines. They then had to spend money on air exchange units to keep the oxygen levels up. The house could have killed them had they stayed shut up in it for a few days. The moral of the story is a little air leakage is not a bad thing for a home, it has to "breathe" some.