We've nearly ended up on the same page :)
The clients care about you nailing the moment. If you miss the moment by faffing about with settings, or being in the wrong setting because you faff about too much, then you have failed.
I think most clients would accept an image that is 90% of technically optimum as long as it is sharp enough and nails the moment, rather than 100% of nothing = nothing. :)
PS, a client wouldn't see the difference between 90% and 100% anyway, nor would most photographers in the majority of situations that matter.
Know and use best practice when you can and have time to for sure. The rest of the time just nail the shot!