Bueller01, Highway 101 north of Trinidad, Calif goes smack dab right through the center of all the towns, except Cannon Beach. So you "can't miss them"!
Avenue of the Giants is old Highway 101. It was bypassed before my time, around 1960. It is not pristine "wilderness" - it has a lot of private property, ranches, busineses, etc even small towns along it. There are some sections which are more "empty", but one rarely feels as if you are out in the empty woods, so to speak - at least the many times I've been on it I don't.
Newton Drury parkway is also old Highway 101 and I well remember when it was the *only* highway, full of RVs, big trucks and traffic! It now does give one most of the feeling of being in the wilderness as there is no private property and/or businesses along it. It's usually very quiet with not many cars. There are many trails that are smooth, level footpaths, true "hiking" is not required ;-)
Howland Hill Road is dirt and narrow, much much slower than the other two and has a completely different feel to it. It's about 6 miles long is all. You get a true feeling of being in a forest of giant trees, as there is no pavement. The road can be potholed and rough in spots.
Having been to all three numerous times, on a tight time schedule I'd opt for Newton Drury. The alternative route is the "new' freeway which is fast, efficient and somewhat boring as there are lots of conifers but few redwoods along it.
As I mentioned in post #4, you will go right through redwoods without ever leaving Highway 101. North of Klamath all the way up to Crescent City you'll be in a mostly redwood-forested area. Then you'll go through younger growth on the long straight stretch between Crescent City and Smith River. By the way - *watch* your speed on this stretch as it's usually heavily patrolled!