not sure if there is some sort of limit as to the number of times you top a plant - but that probably be dependent on numerous factors, including time of vegetative growth phase, etc. maybe you get smaller bud formation, more offshoots, and thus there is a trade-off between number of buds and yield, but i leave it to the experts here to maybe discuss. once those top offshoots grow taller, you can LST or top'em again, etc.
SoG -
Sea of Green where you train the plant's tips and offshoots through a mess at a certain height, to cover the grow area's canopy with vegetative growth. SoG would be a training technique which adds to your vegetative growth phase time length, but then yields most out of a single plant. You'd be topping and LST to fill this screen/mesh.
so, for the same given grow area, you could have 16 small clones straight to flower, or have 4 medium size plants topped or a single plant SoG - as to which is most efficient in terms of time and yield, given the same genetics? also, it comes down to personal preference as to what plant, what growing medium/conditions, how many plants, how to train, etc.
BTW, looks good!!