Highest road in WA: Harts Pass. You need good weather, 4W drive and high clearance. Yep, sedans might be able to do it but they shouldn’t, plain and simple. If you bottom out on this road, you have a LONG walk to town.
Camp: moderately sized sites. We arrived July 1 and only two campsites were habitable due to snow. A bear box would be nice. The landscape is a bit unusual due to beetle and fire damage.