I'm in the planning stages of back to back bathroom remodels. Neither one has a bath fan. My teenage son never opens the window before showering so the ceiling is showing signs of mold spots. They both have attic access with a new wood shake roof. Ensuite is 9x6 and main bath is 9x7ft.

Questions:
Which panasonic ventilation fan would you recommend?
I'm leaning to the WhisperGreen 80 CFM Continuous and Spot Ventilation Fan with Motion Sensor as that would solve the issue of forgeting to turn on the fan before showering. Other options could be same model at 130CFM, or a basic model with a timer switch mounted on wall.

Venting:
Since it is a new shake roof, I would prefere to run the ducts perpendicular across the ceiling joists to the gable wall instead of hiring a roofer to cut holes in the roof. The ensuite run would be 5ft to the gable wall and the main bath would be about 10ft away. The 130cfm whispergreen model uses 6in ducts and the 80cfm uses 4in ducts. To vent to the side wall I would have to go up and across the 2x10 joists, creating 2 / 90 deg. elbows right after the fan unit. I'm thinking of using insulated flex vent pipe. Would this be too restrictive for a 80cfm flow? Should I have to angle the airflow down so there is no condensation worries?

Wiring:
It seems redunant, but does the Continuous and Spot Ventilation Fan with Motion Sensor model require a wall mounted turn off switch or can it be hard wired direct? The only time I think you would need to turn it off would be when cleaning. Does the Canadian Electricial Code require a turn off switch?

Thanks for your expert help.
Dan