I don't know how much luggage you are carrying or how many passengers, but with a Highlander you can put down the rear seat and lay both bikes in, with some sort of foam cushion between them (derailers up and protected from being bent out of alignment. I have an an older Nissan Rogue which is smaller than your Highlander and I have put two bikes in the back in this way. And if you remove the bikes' front wheels you may even gain some extra cargo room.

After decades of rear racks, I bought an SUV specifically to carry the bikes locked in the car. It's also faster and more convenient to load them in and out.

II put an old blanket under the bikes to protect the car from schmutz and grime, and I also cover the bikes on top with a dark blanket to make them less visible to prying eyes.

Just my two cents.