Our 2016 Highlander XLE had a GCWR of 9828# and 5000# tow capacity. We don't travel with a lot of extra goodies, so we were always able to stay under that GCWR. Our 21' loaded for trip as we travel is right around 4100#.
I'm not one who believes I need to be able to climb the steepest mountain passes at 75mph, but we never had any trouble keeping up with traffic or any other problems in the mountains of BC. We also live in the relatively flat Midwest and that is where we end up spending the vast majority of our towing. If I lived in Colorado my decision might be different.
IowaDave and Leon have MANY more miles with their same configurations and are more than happy with the combination. Maybe one of them will care to comment.
Eric (and Mary who is in no way responsible for anything stupid I post)
"Beware of false knowledge; it is more dangerous than ignorance." George Bernard Shaw