I would guess that the 110CFM WhisperWarm would be okay for a 10% bigger bathroom, but really don't have any knowledge in this area. I would think it might just take a little longer to vent or warm up.
I have the WhisperWarm in a bathroom and this is what we did: We put the ventilation fan on a timer and the heater on a simple on/off switch. We figured that you wouldn't need to have the heater on after you left the room, so you could turn it off as you left. The ventilation would be kept on after you leave, so it made sense to put it on a timer. We did not buy one with a light in it. If you interested in that, I think I remember seeing a post that people were not pleased with the amount of light it put out. I have both a WhisperWarm and a whisper fan without the heater (can't recall the name of it) and the fan itself is louder on the WhisperWarm. I would not call it obnoxiously loud, but if you are really particular about the sound level, it might be an issue. If you've read a lot of posts, you will see that ducting is important, too. Use rigid and not flexible ducting. Of course, the heater is louder still.

If your bathroom is larger than the fan is rated for, it just won't be as effective at air changes in that space is it was meant to be. Basically this means it will take it a little longer to do its job. Do you take lots of very steamy showers? If so, you could end up with condensation on your walls or mirrors. My bathrooms are fairly small and the 80 CFM fan is more than capable of keeping even the fog off the mirrors.

The fans are made with separate wiring connections for the features. I did not choose the Warm version of the fan, but still had three possible connections. Fan, Light and Night Light. I only used two of those because that's what my house already had.

I'm nearly certain you can go to Panasonic's web site to download the documentation for the model you're looking at. From what I've read on here before, the Warm fan does require specific wiring capacity to support the heat, light and ventilation functions. Do NOT skimp on those requirements.

If installed correctly, you will definitely be pleased with the fans.

I have a 110 WhisperWarm with light/nightlight combo. My bathroom, with walk-in shower, totals roughly 70 sq feet and it MORE than does the job. You will be fine. just put it as close to the bathing area as you can as that is where most of the moisture it will need to evacuate comes from. As for the heat part - it will "warm" the room a little but really only a standing area within a straight shot of the vents. I also have radiant floor heating, so the combo is like Quiznos ... t o a s t y !!!