I am more partial to the second rims the OP listed. Personally I think 18" or 19" rims (depending on how much the car is lowered) look best on our cars and 20 is just too big, especially on lowered cars. Regardless though, if you are going staggered make sure to get a 19x9 or 20x9 in front, and not 19x8.5 like most of american muscle's 19" rims. I don't understand why they do this. When staggering you really don't want to go more than an inch difference, unless all you care about is straight line performance. Also the 9" width in the front will help with handling.
2014 Mustang GT 6R80, Procharger Stage 2 D1SC, BBK 85mm TB, Boss IM, Sai Li fuel system. Circle D 3C, 1-7/8" Kooks Long Tubes w/Offroad X Pipe, Lethal Over-Axle Pipes, Corsa Quad Axle-Back, Eibach Pro System Plus, BMR K member, Shaftmasters DS, Forgestar CF-5 Wheels and Nitto NT05 tires. Lund Tuned
Lots of suspension goodies and some other stuff I can't remember.