Split the account at the county line, because a Franklin click is not a Donelson click
Metro Nashville and Davidson County run as one consolidated government while the surrounding counties do not, and the buyer changes at that line as reliably as the paperwork does.
A ring drawn around your shop is the wrong shape for a remodeling territory. Drive time in this metro is not symmetrical, and neither is the work. Build targeting from counties and from the routes your crews actually take, then let each one have its own campaign and its own budget.
Williamson County, and Franklin and Brentwood in particular, tends to bring larger scopes, a designer in the conversation and more competitors bidding. Paying more for a click there can be correct. Paying that same price for every click in the account is not, and a single campaign forces exactly that trade.
Rutherford, Sumner and Wilson counties are different again, and Murfreesboro, Hendersonville and Mount Juliet are worth separating from each other once you have enough volume to justify it. Start with two or three geographic splits, not ten.
One setting is worth checking on day one. Location targeting should be limited to people in or regularly in your areas, not people merely showing interest in them, or you will buy clicks from every household planning a move who has typed the city name into a search bar.