Setting level without clipping is pretty easy - turn down the level on the interface just until it doesn’t clip - usually a red clipping light will come on if it clips. I don’t have a Saffire, so I don’t know if that’s done with software or with a knob on the interface itself.
Then adjust the fader on your daw so that it doesn’t clip internally. Pretty simple.
When you speak of effects, are you talking about your pedal effects, or about plug-ins? Not that I want to write a book here, but perhaps I can point you in the right direction with an actual book.