@washugrad, I think you’ll find that that major and school (and their requirements, which will differ by major and school) will be a bigger determinant of how many free classes you’d get than the system (as @ucbalumnus noted)
For instance, isn’t UCSD on a quarter system? That would mean being on the high end of number of classes.
NU being on a quarter system does mean it makes it easier to fit in a double major.
Still, I think you’d find that definitely for engineering and for some other STEM majors as well, just doing the major and study-abroad for a year will eat up almost all your space unless you come in with a ton of AP classes.
I don’t know of many schools where you can study-abroad for a year AND double major AND have a bunch of free space left (unless you come in with a ton of AP credits or are free from distribution requirements like at Echols) regardless of the credit system.