One of the most useful items, for canoe tripping, that you might not know about

Racks can fail, but it’s extremely rare that they will as long as properly installed and used with front and rear tie downs in addition to the straps used with the saddles or J-bars, as specified by almost all manufacturers. Inspect them for any loose or worn parts every time you use them.

If your car has factory rails, use them when strapping down the boat. That way you are securing both the boat and the rack to the car.

Exactly. Tie them down, at the front and back, to the bumper or frame.
Some people don’t. I made the mistake of not doing it on one trip. The rack was secured very well to the truck and the kayaks were secured very well to the rack. I knew it was a bad idea, but I really couldn’t imagine them coming off.
There are now three sea kayaks in the Moab landfill.
My take on what happened is the Yakima towers, which are plastic, were weakened by exposure to the sun. One of the towers broke, which precipitated the whole thing coming off the roof at 65 mph.

2 NRS straps, bow and stern lines on each canoe.
Never/ever a problem; same setup used for multi decades/10s of thousand of miles/all weather conditions, and I’m not gonna change.

Using that system, my wife and I can load/secure 2 canoes in under 20 minutes, Same time for unloading.

My advice is don’t get in too big a hurry, and stop and check “whatever” system you use on a regular basis. I’ve seen bungee cords and ropes snap. Not pretty!

Whatever others use is their decision. I don’t tailgate vehicles carrying boats; that’s another suggestion I offer.