First off, in RM7 on Mac OS the menus are nearly identical to Windows since it's simply the Windows RM running in a wrapper. I merge places and place details after every session where I grab data from external sources.
What have done already is merge all the city, county, state; county, state; and state into single entries. So I have three entries that each have multiple place details under them. So there is Green Cemetery, City, County, State, as well as Green Cemetery, County, State. Fixing that means:
a) Finding everyone using the place name / place detail referring to Green Cemetery, County, State and manually changing that reference to Green Cemetery, City, County, State, then deleting the place detail for Green Cemetery under County, State.
Digging through the DB with SQL and finding the ID for Green Cemetery, County, State and changing it in all references to the ID for Green Cemetery, City, County, State, and then deleting the place detail for Green Cemetery under County, State.
What I really want is a "move place detail" that would allow you move move a single place detail and attach it to another master place. I could probably fudge this by exporting the whole kit and caboodle to GEDCOM and editing it in text, then reimporting it into a new file so it would rebuild the place master and place detail tables. Most of your "unused places" disappear during a drag and drop, although ones that you have geocoded seem to live on.
While I will attempt (if known) to use the historical place name instead of the contemporary one, I make an exception for burial facts so I can create reports with all known people in a single cemetery. I do this as I'm leaving breadcrumbs for those coming after me and you're likely to look for a cemetery in it's contemporary location, but if you were married in county A in 1800, and now it's split to county A & B and that location is now in county B, odds are finding that marriage record will be searching for county A as opposed to B.