so, can answer my own question now...

IAD does have separate choice lines for cars and SUVs

choice line for cars is only up to full size cars
choice line for suvs is only up to standard size suvs

arrived on sep 12, did not pay attention to the models, but both choice lines did just have a few cars / suvs, not a big selectin

could only see tahoes, yukons and suburbans for FFAR category

alamo counter was busy on sep 12, so i was waived over to the national counter
wanted to get a 2015 tahoe, but the agent would only give me a 2014 one
after some talk he offered us an upgrade to a 2015 yukon xl slt with navigation for 10$/day, which we gladly took