Hi all!
I am having a ducted minisplit system installed upstairs, and at the same time, getting a bath fan in my one full bath for the first time. (It has a window to the enclosed back porch currently and a transom window.)

This is what the company is installing:
https://na.panasonic.com/us/home-and-building-solutions/ventilation-indoor-air-quality/ventilation-fans/whispergreenr-selecttm-fan-50-80-110-cfm-multi-speed

The product page says:
Built-in Pick-A-Flow™ Airflow Selector provides the unique ability to select your required airflow (50-80-110 CFM) with the simple flip of a switch. Being able to choose the proper CFM level gives you the flexibility and assurance that one fan will satisfy a range of ventilation design requirements and perform as promised, even with a complicated duct run.

Which I think means the installer picks the CFM at time of installation?

It also says this:
When the fan senses static pressure, its speed is automatically increased to ensure optimal CFM output. This feature provides peace of mind, as the installer doesn’t have to worry about compromising the fan’s performance.

Here’s my question — the company asked if they can install it so it comes on when the light comes on. Does that compromise the variability? Also, I would usually turn off the light when I leave the bathroom. If that isn’t long enough to dissipate condensation, does that argue for having a separate switch?

In the season when we are using the minisplits for cooling, the transom window will be open (and I tend to take not-so-hot showers). But during radiator season, I will be closing that transom.

We just got the transom operating last week, and I have noticed there is no condensation on the mirror when it is open and the window is open. Of course, the tiles in the shower are wet, which the fan helps dry faster, I’m guessing?