Going over 14 from Cedar City to Cedar Breaks is way beautiful. Take in Cedar Breaks Monument. There are lots of dirt roads easily ridable in and around Navajo Lake, Duck Creek Village area. At 9K' it is also cool up there. Could probly get a cabin at the lake. Then there are dirt roads going south, along the eastern border of Zion NP. Or ride it the other way from my next segment below. Hiway 14 re-opened last year after a slide close it in 2011.
Coming the other way, from 89 near Kanab, nice dirt route from east of there Johnson Canyon Road, puts you up and west towards Duck Creek - Navajo Lake - Cedar Breaks. That's the way we came from North Rim last year on our GC trip - RR in my sig. We have the route laid out in the report as well. About 600 miles of dirt roads, camping off the bikes, north rim to Dixie Forest.
The Kaibab Plateau and national forest is absolutely beautiful. Some elevation and trees so it's cool, lots of dirt routes. Highlights are Bar-Ten Ranch, Toroweep, Sublime Point. Ride out to Sublime, then over into North Rim to the big lodge. Cabins there too. "Kaibab", a Piaute indian name which means 'mountain turn on side'.
90% of GC visitors reach the area from the south, so the north rim area gets very little tourist pressure. We pretty much have the place to ourselves when traveling through.
Can't help you with Bryce Canyon, but see and hear it's really scenic.