Will it make my house look dark?
Not with a clear film.

I've been putting film on home windows since 2001, and the complaint I hear most is the same: "The sun's ruining my floors." UV light coming through the glass is a big part of why hardwood, rugs and furniture fade, and Florida has plenty of it.
The films I install for homes are SunTek, backed by Eastman. Most folks want a clear or low-reflective film, the kind you'd have a hard time spotting from the street, so it doesn't change the look of the house. If your neighborhood has a design review committee, I'll give you the spec sheet to show them. They make the call, not me.
How it works: I come out for a free estimate, hold samples up to your own windows, and tell you straight what I'd put on them. Then I install it myself.
Have beachfront windows? See sea turtle window film.

Not with a clear film.
Many do; I'll give you the spec sheet, they decide.
Lifetime warranty on all residential and auto work.