If you want the items in the Favorites List to be active only when you are within the jurisdictional boundaries of the system to be monitored (approximately), then set Location Control to On. (The rules of the database are that locations and ranges of Departments have to approximate the geographical area of the jurisdiction.)
Leaving Location Control Off means the Favorites List is always being scanned regardless of where you are.
So for example you create a Favorites List that has Dothan and Enterprise Alabama "stuff" programmed. If Location Control is On, then when you are in Dothan, the Enterprise "stuff" is off and the Dothan "stuff" is on. If Location Control was Off, then when in Dothan the scanner will attempt to scan both Dothan and Enterprise.
The deciding point is do you want to try receiving things as far away as possible at a cost of scanning channels that might be out of range?
"Hold time" is the amount of time the scanner lingers on a system before it moves to the next system. Or the amount of time it will wait for someone to talk. This is a user option and to each his own. The deciding factors are how much time do you want to spend on one system in hopes of receiving a transmission? I use the default value.
("Channel Delay" is similar - it is the amount of time the scanner lingers on a given channel after a transmission finishes, to wait for someone to reply. Again a user preference thing.)
I'm unable to explain the lat/long discrepancy. I don't make any changes, using whatever Sentinel downloads from the database. I haven't had any issues that I'm aware if,