Try to put little stock into what others are setting their units up to. Unless your hunting with them in the same area, someone else's settings may not do you any good at all.
You have to use the setting you feel most comfortable with. With all due respect, it sounds like you want your cake and eat it. If your concerned with maximum depth, run it wide open. Don't let the depth thing get in your way to making sensible settings that will make your usage far more productive.
With that said, why not try a little test bed, or perhaps some air test ? Granted were not hunting coins in the air, but one needs some means of understanding of how, and what the adjustments affect before going into the field. Would this be 100% correct, no but it will set you in the right direction. Best may be just throwing down a few coins on the ground your going to hunt on, and see how the detector will react, then & there to your adjustments. This will put you close for hunting in that area. I allways have a small box nail with me I throw down on the ground to set my low end discrimination with. If I deceide to notch out anything, I do it after finding the items in the place I'm hunting. Trash like pull tabs react differently, in differnt soil. The need to set the notch for them is importaint to do right there.
After a while it will all come together, and you will end up with a few favorite settings for the areas you hunt.
Good luck, I hope this helps you find plenty.