Doesn't matter if you do straight 12/12, 24 hour darkness, etc... its going to take the same amount of time regardless... if your planfs are sexually mature and READY to be fljpped, it should only take about a week before your biologically in flower. If the plant is still young, and not sexually mature biologically, then it can take a solid 2 weeks before she goes into flower mode biologically.
Myke brought up flowering taking a month outside to transition... thats because the light cycle changes so gradually, and you need at LEAST 14/10 usually before a plant will start the process of flowering biologically. 1 extra day of darkness, or even 2 likely won't speed things up much, but sitting JUST on the cusp of flowering light cycle for several weeks wefinitely slows the process down (outdoors).
As for SCROG, I usually keep going for roughly the first 2 weeks of flower... its moreso about keeping the canopy even so light distribution is maximized and nothing gets shaded out. Whether or not you achieve that by weaving under the net, super cropping, LST, or all 3 combined is personal preference