it seems the normal consensus is to crush grains fine to get better efficiency but this is not my experience, in the 70s my father taught me to brew and course crush so the grain is broken and the husk is not ground up, this has always worked for me. I used to get mid 80s MHE with a good sparge until I found out about vorlauf, I built a small pump to hook on the side of my boiler/mashtun with the receiving pipe aimed in the middle of the tun and whirlpool the wort and send the outlet pipe over the basket of grain (raised on a frame out of the wort) until the wort comes reasonably clear, then follow up with a sprinkle sparge. I am not adverse to turning the grain bed to get the sparge through the grain and get consistently well into the 90s MHE. many say this should wash out tannins but I haven't noticed this.
my system is a 40lt boiler through which I rotate a basket of grain in the wort to maintain a constant temperature, I start with 25lt of water, stir the grain well and start it spinning for 60 mins, stir well again and test for starch, I then raise the basket and vorlauf, then set to boil and begin the sparge until I have 32lt add the hops at boil. I generally use the grainfather app to work out brew house efficiency. for me the biggest influence on BHE is the Lauter process not grain crush or mash thickness. in my process the mash is very thick as most of the water is outside my spinning basket and I just need to make sure there are no dough lumps and the grains are saturated, that course crush helps in this respect.