Warning -- you definitely DON'T want to put vapor barrier on both sides of a wall, it will trap what moisture does seep in. If not using hard foam, will compromise insulation, and in any case will promote mold. Mold will not harm wine, but you don't want it in house.
The Gold book is very useful. Every situation is different, so hard to give blanket recommendations. My situation doesn't sound dissimilar to yours, this is what I did.
I framed a corner of basement - built 2 walls and used two preexisiting rock walls. In two walls I put r-24 fibergalss, sheetrocked inside and outside, inside plastic vapor barrier. Vapor barrier against rock walls (probably unnecessary, but figured wouldn't hurt). R-30 in ceiling. An insulated exterior door would have been first choice, but because of pipes outside space too tall. So I cut down an interior door, installed, drilled holes, and filled with spray foam. Weatherstripping all around, spray foam in every wall gap (112 year old house, had to built around pipes, beams, etc. ). Betsy was worried we were losing basement space, so I put shelves on exterior walls.
Below grade, keep steady daily temps. Slowly ranges from 52F in winter to 66F (at top) winter. During a couple of protracted heat waves temps up top approached 70F. Probably not a big deal (see Robin's report on the chai at I believe Ch. Margaux), but to be safe this year I put an old room AC into wall. During heat waves I run a couple hours per day, keeps things around 65F.
One can choose to "trick" an AC to go colder than 65F by faking out thermostat. I wouldn't worry too much about AC taking out humidity if it's only running for month or two in summer. Low humidity is a real worry in dry climates, but I doubt you would have a problem in KY (unless you tricked an AC unit into keeping cellar at 55 for 12 months).
Other big decision is racking. I use a combination of "grid" racks (the Wine Enthusiast black tie ones are cheap and effective), stacked OWCs and milkcrate bins, and some plywood bins I built myself. Bins give you more bottles per sq foot, but aren't especially good if you have a lot of one and twos.