hate to put it this way but it's really simple man....
SPLASH GUARD - guards against splash
If you don't have anything you splash through that you don't mind getting everywhere in your engine bay or the potential of your tires picking up little rocks and throwing throwing them into your fender, go for it.

simple solution for the little plastic screw is to "roll" the little tab that it sits in up into the fender with your fingers. Push it up about 1/2"-3/4", it will be obvious when the fender liner can't go anymore. Mine used to rub any time I turned, I did this and it has not rubbed since.