Ooh, I was thinking the straps would break first, but I think you hit on something with the roof racks!
Usually they're only rated for like 100-150lbs, and that's going to put a lot more force on them when it turns. They might not even make it out of the parking before something starts to come loose!
Hm... Flower vapes certainly reduce the odor, but they do still smell a bit. If you're looking for absolutely minimal smell, then vape carts and edibles are probably the way to go.
That said, I'm by no means trying to discourage you from trying dry herb vaping! It smells way less than flower, and doesn't linger the way that smoke does. I'd recommend against getting an expensive top-of-the-line flower vape to start with, though; a cheaper entry-level one is a good way to figure out if it suits your needs (and, if it does, to figure out what features you want to prioritize in a nicer one).