Bottom line is EAs sliders are broken. I too have encountered sweet spots like on roughing the passer, 1 click more than the sweet spot and its a flag fest. I do try penalties at default and at extremes to see what happens, but I don't test every click in between.
I know the holding slider is broken and doesn't work. In fact upping it seems to make them block less like they try to avoid the penalty causing more issues.
EA really needs to have one of the slider guys from OS come to their place, and show them exactly what is wrong and what sliders don't work.
I am sure the penalty sliders have an impact on gameplay, but to what extent is unknown. There could be some magic potion perfect combination, but to find it you'd have to test 5 games on every combination one click at a time. Good luck with that.
I am pretty sure EA doesn't even know what sliders do. A couple work, but most of them are broken, backwards, ore just placebo.
They need to be revamped and they need to have it where 0 means none and 100 means every play and let people adjust from there.