Acetaminophen is 20-50% plasma protein bound & the absorption process occurs by passive transport. What does that mean to the average A. frequent user?

Nothing. It means you need to comply with the limits that the manufacturer recommends. How it gets into you and how it rides around inside of you has nothing to do with how it can ruin your liver overnight if you swallow a fistful. 3000 mg/day is safe; obviously you're going to take it in divided doses.