No. And No. Tall ceilings are awesome, especially in bathrooms. Just have lighting. No need for a soffit. A tall ceiling in a small room can add drama.

No soffits. Lowering the ceiling depends on the space. If it is a small bath then a tall ceiling might make it seem like you are at the bottom of a well. If a larger space with big windows it can seem grand. Regardless I would use side lights for vanities.

No! I recently raised my ceiling in my bathroom redo so I could have taller ceilings! Are you doing windows? bring in a nice pendant lighting and sconces. plenty of light. If you want to see mine click on my name, bath redo.

And, you could always do a dark dramatic color on a ceiling in tall room.