I can speak to the FX and the Quick 1. I found the FX to be a bit more upright than the Quick 1. That being said, the Quick 1 is a great bike and can hold up to it's name.
As for size, I'm 5'6" with a 29.5" inseam and ride a Medium Quick 1 without a problem. The Trek FXs I tested out before the Quick 1 were also mediums.