I voted intermediate. But with the "at your peak", and the "dominate" phrasing, I am voting perhaps more conservative than my ego.
Living in Louisiana, whitewater always required travel and planning. The Cossatot River in Arkansas was our closest ww. The 16' BlueHole was rigged with a massive chunk of styrofoam held in by the center thwart. Always tandem, as none of us had solo canoes. We would group up with 2 to 6 boats. Mostly to gain the experience from others. Was too dangerous to attempt without others.
Watching the weather forecasts, and the river gauges, we had to time when the river was running. Six to 8 trips a year was a good season for us.
Cat III, IV, and V was the usual after a good rain, but might not last more than a few days. The river is about 89 miles long, but only about a 14 mile stretch is considered ww above a class II. There is a section that drops 40 feet in less than 1/8 mile.
Never got to the skill level to be able to be defined as being able to "dominate" in above class III. Smiles and grins, yes. But the pucker factor rarely diminished. I learned the value of a good PFD.
But that was in the early 70's, through the 90's. We eventually became the "older guys" with the experience. The foam has been long removed from the Blue Hole, and my ability is, I am sure, better in my mind than actuality. I have not had the desire to get bruised of late. Good memories will have to suffice.