If you go into the 5 string Jake, to the hardware screen, and switch spacing, 19mm is either standard big or one of the 6 hipshot options, if you go to 18, its F style or monorail + the hipshots, and 17 is "standard" or monorail, plus the hipshots.
I have never even thought about a bridge before, so I am pretty out of the loop on what they all do. After some research into aluminum v brass, seems that IF there is a tone difference, I would prefer aluminum, but I play a P with the tone off and flats, so I doubt I'd notice anything on that end. So if there is adjustment, and... well it holds my strings I guess I don't care too much, but there isn't alot (or any...) info on the non hipshot options.