Scotch Locks are a mechanical way of connecting wires.  They are faster  to install than a fully soldered and insulated joint. Using Scotch  locks reduces labour cost on jobs. Hervey Bay Auto Electrix has repaired numerous installations where the mechanical join has failed.
Hervey Bay Auto Electrix does not use or recommend Scotch Locks.

Providing power from the main battery to run appliances, charge caravan  batteries, run winches, fridges, etc has become common practice.
An isolator is recommended to disconnect all power drain from the main battery when the vehicle is not running.
An isolator automatically disconnects all batteries and other devices so that the main battery will have sufficient charge to start the vehicle.