Danny,
we stayed at Watchman in Zion last October, got lucky and got the last available campsite. first come first served. Campground is basic (water and electric only if I remember correctly) but views are spectacular. You can take the tram from the park into the canyon where there are TONS of hiking trails. The tram stops regularly and lets those that want to hike or just site see off or back on.
we took the tunnel to Bryce and as rmmpe says it is "escort". Actually they stop traffic one way and let traffic the other way go through. Short delay between directions. Unfortunately we were unable to stay in Bryce and had to keep going last year.
Haven't been to Cedar Breaks