As you have 5 people, I seriously doubt ANYTHING smaller than the Exp will work for you, especially if you want/need 3rd row seating for normal people. The Grand Highlander is a BIG step down from the Exp, and it's 3rd row is cramped. In fact, the entire vehicle just feels cramped, test drove one about 6 months ago, before getting the 2019 Expedition Plat. The Grand Highlander has this huge center console, which intrudes into your seating area, so that your right leg is ALWAYS touching it.
I would do what other's suggested, and get an Extended Warranty. And get some more comfortable tires (not performance tires which will be harsher for sure), and lower the tire pressure a bit, maybe 2 PSI below recommended. Shouldn't affect much in terms of tire wear, and will help it be more compliant. Getting 18's may help, but if you're complaining and you have 20's, then it may not be worth it. We have the 22's on our Expedition. Over the ride is nice and comfortable. Not to the level of isolation/comfort as my 2011 Lexus LS460. You CAN feel really bad roads, but this is a truck frame, not a car.