You can customize the leveling speed for Adaptive Difficulty in Rocksmith+ through the game's settings.

To change the leveling speed:

  1. Open the Settings menu.
  2. Select Game Options, then Gameplay.
  3. In the Difficulty Settings tab, select Leveling Speed and adjust the speed to your preference.

You can choose between Slow, Normal, or Fast.

Please visit this link for the most current information.