One of my suppliers like the Kohler one-piece shower units.
I've installed Lasco, and I would say they're ok, but not something to brag about.
For fans, I would think something in the 90 CFM range would work.
If you're using a fan/light near the shower, I would have it in front of the shower and center it.
I wouldn't put in within the shower. Why have the sound of the fan in your ears. I like the Panasonic fans, very quiet and easy to install.
For tubs, I like some backsplash where the wall meets it.