#2
?not sure what you mean by adjusting the action.

Single locking, locking nut at the top of the neck.
double locking, strings are locked at the locking nut, and locked into the bridge behind the saddles.

non locking is like a standard strat, where there is no locking nut at the neck, and the strings are simply held in place by the ball ends. They aren't locked at either end.
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