People don’t realize how big the western states are. Most states are bigger than a lot of countries. For my honeymoon years ago we went to Carlsbad Caverns, starting from SLC. We went from Salt Lake City to the Grand Canyon to Roswell to Carlsbad, then to Denver and back to SLC. It was a looooong drive and I did it in a week, but I don’t know if I’d do it again ever.
Anyways, all of these suggestions are really good. Do consider that June, July, and August are peak visiting times for all these places, so there will be lots of crowds. Highway 101 on the Pacific coastline is a maze of twisty little passages, all alike so the drive is really slow.