I've never ridden the event, but have ridden the roads.
The Century has lots of bike path and big shoulders, very safe. The Metric has little / no shoulder for a lot of it, but you'll see about 10 cars the whole time on most of those parts. The only part that is a little sketch is coming back on the RIver Road, there is no shoulder and there is some traffic. It's OK-enough.
The 40 mile has no shoulder and light traffic, and is flat. All routes have good views. The Metric is probably harder than the century, there is a pretty steep climb. If the weather is good, the Metric is probably the best route in terms of scenery, interesting riding, climbing, but it does go quite high, so if there is potential for bad weather the Century would be better.
Camping in the area:
I would try out on 313 myself - it's really beautiful out there. Also there is BLM Camping at Indian Creek (an hour south on 211) or out on the La Sal road, but that might be restricted now.
While you are there, I would recommend riding the Arches road out and back from town.