What more power could have done for Nelson and Rodney

How would substantially more installed power have changed Nelson and Rodney's wartime employment?

The extra speed could have trapped Gneisenau and made it plausible for Nelson or Rodney to fight at Denmark Strait.

Additional machinery would change operations rather than merely improve trial speed. With roughly one-third more installed power, a Nelson-class battleship might have prevented Gneisenau from escaping an earlier encounter. Greater speed would also make Nelson or Rodney easier to integrate with the force pursuing Bismarck. One of the pair could then plausibly have joined the Battle of the Denmark Strait, radically increasing British heavy-gun strength there.