Do I need to scale my models HUGE before using BoolTools?

Nope!  BoolTools is optimized to work with smaller 3D printable models (but also works for big models too)

Scaling models to 1000X or more before using various SketchUp tools (and then scaling back down) is also known as the 'Dave Method' (made popular by Dave Richards).  This method should not be required when using BoolTools but is often needed when using the native SketchUp solid tools.