I would like to apply a keyboard shortcut to a preset

You can't assign a shortcut to an effect preset. The fastest way to apply a preset is to drag and drop it from the Effects panel.

If you’re working with a clip that features multiple speakers in the same shot, a practical approach is to stack duplicates of the clip in a multi-camera source sequence. Apply the position and scale settings to each duplicate to frame each speaker individually.

When you bring the multi-camera source sequence into your timeline, you can use the 1-9 shortcut keys to switch easily between the different speakers.