YMMV but some stations will hold you to the letter of the reservation and some won't. I've experienced it both ways where reserving the most expensive class, I was allowed to select from other vehicle classes or not.

For a luxury SUV, the ones you listed are most likely for that sort of reservation (Cadillac/Lincoln/Infiniti). Q7 is rare, haven't seen any X5s in a while, XC90s are there, haven't seen any of the MB products at National (Hertz has them), A6 is in the fleet, 5er is in too.