Are you asking as the driver or as the passenger?
I not only have fear of heights, but also overly-sensitive with centrifugal force...driving (or riding) curves. Maybe an inner ear problem. I feel like the whole motorhome is going to fall over. I cannot be the passenger. Way too scary. Even as the driver, I won't turn my head off the road in front of me while on a curve. My eyes can go left and right, but not my head. So that's how I drive while in the mountains and while on curves...focused on the road right in front of me. At least it makes me feel more in control than being the passenger. Luckily, I have a co-pilot who points out things when necessary.
All this being said...I am a good driver, albeit slow and cautious.
The thing about fear is that it's mostly in our heads, and not reality. Most likely, all the roads you choose will be safe roads that thousands of other RVers drive on. And remember, the discomfort will only last for short periods of time, compared to all the great experiences in beautiful scenery.