Different systems and different approaches will all deliver different results.
In my case, I hand mill my grain, with the gap set at 1.1 mm. I get a little flour, but not much.
I use rainwater, and make water additions based on BS2 for the style I'm brewing.
I stir vigorously at dough in, and again when I add my mash out prior to run off. I batch sparge, and again stir vigorously when I've added the water. My run off and sparge start immediately, I don't wait. I use a small 25m litre cooler, with a home made manifold.
My extraction efficiency is regularly around the mid 90%, and occasionally over 100% (yes, it's possible).
The real key to brewing consistently is to get to a point where you can reliably produce your results within a small parameter. That makes recipe design and hopping schedules easier than having to adjust on the run.
For what it's worth, I've done decoctions, and found no difference in my results. Maybe it works for others. I don't bother these days, as a brew day is long enough as it is.