@jcisthelight I love this idea! In my opinion Utah is best experienced in the Spring or Fall since it can get REALLY hot in the summer. I would highly recommend checking out Idaho that time of year. It's a little less crowded than popular hiking spots in Colorado, but just as gorgeous.
If I was planning this trip here's what I'd do:
My suggestion would be to fly into Boise and do a short hike there on the day you arrive, then head down to Stanley. There are a TON of really incredible hikes in the Sawtooth Mountains in that area, it's truly breathtaking. Depending on the length of your trip I would suggest doing multiple nights in the Stanley area since there's so much to see, and you could also have a more chill day at Redfish lake and rent paddleboards or something.
From Stanley, I would head to Sun Valley. It's a fancy resort town with a ton to do, it would be a great place to splurge on a massage or something along those lines. You could hike up Baldy (the ski mountain) or head back up into the sawtooths for more hiking since it's not that far.
Once you're done in Sun Valley you could head out to Craters of the Moon which is pretty cool, although it will also be uncomfortably hot that time of year and honestly that part of the state isn't as scenic to drive through. You could also just loop back to Boise and either do more stuff in Boise or catch your flight home.
I LOVE Idaho and I had a lot of fun writing this out, feel free to DM me for specific suggestions if you actually end up doing any of this.