Man, that 4-7-8 pattern sounds like a workout for my brain more than my core. In my experience, focusing on breath ratios turns my plank into a panic attack because I lose count halfway through. Your mileage may vary, but I usually end up holding my breath and turning purple instead of engaging any abdominals. Take this with a grain of salt, but I think my transverse whatever is more confused than zipped up. It's impressive if you can manage it, but for us mere mortals, just breathing without passing out is a win. Maybe I need to practice more, but right now, my core engagement is more about not drooling on the mat.