Bid the city and county apart from Douglas and Jefferson, not with a slider
Location bid adjustments average away the differences that decide profit here, and separate campaigns put them back on the table.
Denver is a consolidated city and county. Douglas County, with Highlands Ranch, Parker and Castle Rock, is newer stock and a different job mix. Adams County, running through Thornton and Westminster, behaves differently again. Older central neighborhoods send service line and repipe work that a newer subdivision rarely does.
Roll all of that into one campaign with location modifiers and you get a blended cost per click that tells you nothing and a budget that drifts to whichever geography clicks most, which is not the same as whichever geography pays most.
Separate campaigns cost you data density and buy you control. Separate budgets, separate schedules, separate negatives, separate ad copy naming the places you actually serve.
Start with two or three splits, not six. A shop dispatching from one yard usually cannot support a campaign per county without starving all of them.