Davidson and Williamson deserve separate budgets, not one metro radius
A single radius drawn around downtown spends the same money on two buyers who convert at different rates and pay different average tickets.
Start with geography, not keywords. Build separate campaigns or separate budgets for Davidson, Williamson, Rutherford, Sumner and Wilson. Each gets its own bids, its own copy and its own reporting line.
The reason is drive time and job size. An estimator sent from Green Hills to Mount Juliet has spent a morning. If the average job in one county is smaller, the ad cost that county can absorb is smaller too, and a blended report will never show you that.
Use location targeting set to presence, not interest. Otherwise you pay for people researching from out of state, and in a metro with constant tourism traffic that leak is not small.
Bid Franklin and Brentwood knowing the buyer profile differs from East Nashville. Same product, different objection, different landing page. The account should reflect the difference rather than average it away.