I have used tray style hitch mounts, the cheap car trunk racks, Thule roof racks, homemade pickup racks, and yakima roof racks.
My preference?
1. Yakima roof rack. Can be used to carry multiple bikes easily, quick on and off, can use trunk easily while bikes are mounted, don’t have to remove for driving around and easy to remove anyway. I use one frontloader rack for the mtb and a fork mount for my road bike. Plus, I bought the whole setup (towers, rails, clips and three racks) for 100 bucks. I’ve also used the lockjaw mounts, which worked fine too and you didn’t have to take the front wheel off for those either. The only con? Fatbikes. But I don’t have a fatbike so the yakima roof set up is great for now.
2. Close second is the tray style hitch mount. The good ones can be lowered so you can get in the trunk. the downside is that they are incredibly expensive and the cheap ones suck. Everyone here in MN who has a fatbike has a truck or a hitch mount.
At the Lutsen 99er last year some guy had strapped his fs carbon xc bike to the roof of his Nissan 350Z. He used a ton of carpet and mats, but seriously….