Trigger 1 is very simple, but has the problem that once the trigger is pulled past the first restraint (U shaped hoops), the load on the trigger line will cause the trigger to pivot around the remaining restraint. For table top models though this can work quite well.
Trigger 2 uses a hook that holds the trigger line and which can be pivoted around to release.
Trigger 3 is a modified Pelican hook and can result in a very easy to release trigger (low trigger pull.)
Trigger 4 could have a line attached to the upper end so that the operator can be standing well away when the payload goes whizzing by.