The problem with most people's guillotine game, is that they defeat
themselves before the opponent does.
When some folk say things like 'guillotines are low percentage', it is very likely, the picture in their minds is someone getting a front headlock, then trying to finish by pulling guard; which of course, is going backwards. Not only does this drastically reduce your potential for finishing, it also leaves you in a bad position if you do fail to finish.
In order to make front headlock attacks work best, you can't do it in a, for lack of a better term, 'ibjjf' manner, you need to do them like a 'fighter' or 'wrestler' would do them; not simply as an dimensionless 'submission move' that you go into regardless of what you and your opponent's relative body positions are, but as an implement of control used to advance into more powerful (finishing) structures. When watching examples of successful front headlock chokes at the highest levels, a clear trend starts presenting itself; the significant majority of finishes come by way of pinning the opponent on their backs first, giving themselves a fulcrum through which force directed into popping their heads off is exponentiated. If you can trap the arm between your ribs across their neck as well, that pushes up your finishing power even more.
One can possibly speak of other more specialized details, like outside in throat grips or elbow deep gag grips and so on, but that is the more basic essentials.