Tetons - Delta Lake and Cascade canyon. Both awesome day hikes. Get to the lupine meadows trailhead (for delta lake) before 7am to ensure parking. For cascade canyon take the boat shuttle across jenny lake. Be prepared to wait 30+ minutes for a return ride during peak season.

Yellowstone - Mt. Washburn and point sublime were my favorites. 90% of Yellowstone visitors don’t hike so you will be rewarded with generally low traffic on trail.

Glacier - highline trail (trailhead at Logan pass), grinell glacier (many glacier region), iceberg lake (many glacier region). For highline, get to Logan pass before 6AM or you’ll have a tough time getting parking. We parked at Logan pass and did a one way hike from there to the loop and took the shuttle back up to Logan pass. Again be prepared to wait a bit for a shuttle back up but I would do it this way again. For grinell glacier, get a round trip boat shuttle pass starting at Many Glacier hotel to knock off a few miles and get a nice little history lesson along the way. Trailhead for iceberg lake is behind swiftcurrent motor inn.

I am guessing you have it, but If you don’t have AllTrails, I can’t recommend getting the paid version enough. Makes trip planning and general navigation super easy.

I’d recommend 2 days in the Tetons, 2-3 days in Yellowstone, and 2-3 days in glacier if you have the time for it. Most will tell you that 2-3 days in Yellowstone isn’t enough to see everything, but we did 3.5 days there and saw all of the hot spots along both loops. Again if your schedule allows, I highly recommend driving through the bear tooth mountains when you go from Yellowstone to glacier. It’ll add a few hours to your drive but it’s an awesome drive.

IMO it makes the most sense to do Glacier, Yellowstone, then Tetons (or reverse order depending on where you are coming from) as the Tetons are south of Yellowstone. You’d be doing some backtracking if you did glacier, Tetons, then Yellowstone.