Third Leg, Colorado Springs to Poncho Springs to Grand Junction. Expect this to be very scenic. Distance is 305 miles. Any suggestions?
It's a great drive where you travel alongside the Arkansas river to Poncha springs before going over the continental divide at Monarch pass to the Gunnison river through the Currecanti Nat rec area towards Black canyon. All are worth stepping out of the car to 'smell the roses'.

4th leg, Grand Junction to Moab, UT, about 113 miles. Now, could I just see sights (no hik8ng plans) in the rest of day, should I spend 2 nights in Moab or by Arches Natl Park?
When you leave GJ take a small detour to the Colorado National Monument and experience the Rim rock drive, an amazing drive often overlooked. (check current conditions)

It has been mentioned but I will also recommend getting off I70 for UT128 through Castle valley to Moab. No real time loss but a lovely drive through the canyon alongside the Colorado river. With this in mind I would spend 2 nights in the Moab area to take time to drive around Arches NP and the Island in the sky area of Canyonlands NP where you can drive all the way down Grandview point road for a great view ! Be sure to stop at the Shafer trail viewpoint and Mesa Arch for more amazing views for little effort.

If you are undecided where to next, I would take UT24/scenic12 to Bryce canyon, it's amazing and will take you to Capitol Reef NP. Ruby's Inn at the top of Bryce canyon is a lovely place to stay and perfect for a drive along the Bryce point road with many scenic viewpoints a few steps from the car. To do this, head to the far end of the canyon and stop on the way back up, all the viewpoints will then be on your side of the road. Make sure you pack warm layered clothing as Bryce is at high elevation and it gets pretty cold up there, is it worth it ? OH YEAH!!(Check conditions)