Stefan -
I live in Wyoming, taught college in Montana.
Have biked almost every paved road and many unpaved roads in both states.
I've done 8 major tours of the West up into western Canada and all the way to Alaska.
2005 - in the early days of digital
https://www.crazyguyonabike.com/doc/?o=3d2&doc_id=1168&v=sMFirst - if given the choice between the Canadian Rockies and Skyline Drive it's no even a choice.
If you are from Germany, Skyline Drive is like riding in the Harz and about as busy.
Icefields Parkway is moderately busy, but there are forest roads you can take that are incredible.
Think of the Hohe Tauern without all the development and people.
From Jasper you can take the train to Vancouver -
Or continue west to Prince Rupert and Haida Gwai - home of the Haida people.
Then take the ferry south to Vancouver Island.
Next - Mid March is kinda early ro start - especially when you hit the high elevation in N. Arizona.
Flagstaff's average temps for April 1 are 12C / -5C with 45 cm of snow in March and 18 cm in April.
Total winter snowfall of 225 cm - most of which will still be on the ground.
Here's a website with climate info for the western states - (in Fahrenheit and inches)
https://wrcc.dri.edu/Climsum.htmlThe North Rim of the Grand Canyon does not open until May 15 - which is probably too late for you.
But it indicates how much snow there is and how long it takes to melt.
And the North Rim has only 10% of total tourist visitation - and is magical.
Still, the South Rim is gorgeous and has hiker/biker campsites.
During the North Rim season you can shuttle you bike/gear and hike across the canyon.
I'va done it almost a dozen times - but you will be too early.
You should see if you can hike down to Phantom Ranch from the South for 2 nights and explore.
Arizona does not have many paved back roads - even unpaved roads that are good choices.
And because Arizona is growing so fast, the traffic can be iffy.
Hwy 87 - esp. north of Payson is 2-lane, mostly without shoulders.
Plus it has heavy traffic (20,000 AADT) and you will be climbing.
(The last time I did it I was going south/downhill. AADT - average annual daily traffic)
US 89 north of Cameron has a feature that is very dangerous for cyclists.
It is a 2-lane highway with wide shoulders - BUT -
Whenever they have a passing lane it uses up the shoulders on both sides.
Plus, there are deep rumble strips on the tiny shoulder that remains so you have to use the lane.
But. cars & trucks are going extra fast to pass. (9000 AADT)
The speed limits on these two roads is 65 mph (105 kph) - but most people go 75 mph (120 kph).
My sense of AADT -
Less than 1000 - Excellent
1000-1999 - Good
2000-2999 - Fair, shoulders helpful
3000-4999 - Poor, shoulders needed
5000+ - Difficult, shoulders essential
Others are more comfortable with higher traffic and narrow roads.
Hwy 89A north of Sedona is very scenic, but very narrow.
Plus you usually have a guardrail or rock wall right on the edge.
So you can't escape off the road in a difficult situation. AADT - 6500-7500
It is also very scenic for drivers - who may not be looking carefully for cyclists.
The one good thing is that the speed limit is 40 mph (65 kph).
Major construction on the Oak Creek switchbacks thru 2023.
Connecting to Kanab, Utah - especially if the North Dim is still closed -
US 89A will have much less traffic iwth a lovely crossing of the Colorado at Marble Canyon.
A bit tougher, with a good deal of climbing & switchbacks to the upper plateau.
But the downhill to Fredonia doesn't have many tight curves and you can fly.
Should stop here and talk about other states later, if you wish.
Best - Juan
Google maps pix of each tough highway section.
Pic in the inner canyon of the Grand Canyon - 2019 tour.