Hey Lon, I should let Marylynne speak first and I look forward to her contribution. But I can’t help piping in on the question of accessing the lower road.
From the top at Island in the Sky in Canyonlands it’s known as the Shafer Trail. Below the steep switchbacks a road enters from the left, specifically that’s Potash Road which starts just past the Colorado as you head north from Moab. If you continue past the Potash turnoff, it turns into the White Rim Trail.
Though I’ve seen rental cars in there, you have to be extremely careful about muddy or icy conditions, even when you have good ground clearance and 4WD. Continuing on the White Rim Trail to it’s intersection with the Island in the Sky Road north of the park entrance is most definitely 4WD in it’s last few miles. On top of that, driving the length of White Rim requires a very long day.
Sedans might make the Shafer trail descent through the switchbacks from Island in the Sky. Note I said “descent.” I wouldn’t drive a sedan UP through the switchbacks. It can be passable to sedans if recently graded, but between gradings can built up rocks and cobble too large for low clearance sedans. Meanwhile you CAN most times enter the area on the Potash Road and drive to the base of the switchbacks on Shafer Trail. You can also drive a fair distance out White Rim Trail in a sedan.
Great trip obviously. I don’t feel that I’m hot spotting in posting this, because the info is readily available from the NPS and myriad sources in Moab. But as noted in Marylynne’s other recent thread on the switchbacks, local knowledge can help keep you out of trouble.