Smokey mountains and Blue Ridge Pkwy

That is a rather big area, so I think your need for reservations is going to depend on where you are planning to camp. The NP campgrounds in my area here in central Virginia vary widely. At the Otter Creek campground, no reservations have been needed for some years, and none were possible anyway. This coming season, it will be possible to reserve a site, but I don't know that doing so would serve any purpose, unless you knew you wanted a particular site. On the other hand, Sherando Lake is extremely popular, and Thursday through Saturday nights, all the reservable sites are usually booked up weeks in advance. There are 25 first-come sites, but to get one, you pretty well need to be at the gate by 9 am or so Thursday morning, otherwise, you are at the mercy of someone having to leave unexpectedly. Sunday through Wednesday, however, no problem.