Take it easy and enjoy the views... the Smith River canyon is beautiful.
Mostly downhill on the California side. Be aware. there are some
narrow highway lanes westbound just before Patrick Creek... about 1/2 mile.
Truck drivers go through there ok... so I imagine a 35' fifth wheel will fit just fine.
You have a choice, just after Hiouchi... (Jed Smith Park).
Just before the bridge... If you go to the right, the road is easier.
Go to left, and you have some tight corners going through
the Redwoods. IMHO: Nothing you can't handle in a 35' fifth wheel.
Either way, you end up on 101, and then turn south!
BTW.... through the canyon... use turnouts if you are holding up traffic.
Other drivers will appreciate it!
Couple things to do on 101.
1) Take the 'Newton B Drury' parkway. South of Klamath river.
That is the name for the 'Old Redwood Highway' old road goes through some of the greatest northern
Lots of turnouts, trails, photo ops there (etc). May spend all day there.
At the south end of the Drury is 'Prairie Creek Redwoods' state park.
It may be booked full, but that is a wonderful place to camp.
Lots of elk in that country... you will probably see some... but don't stop in the road. There are a number of accidents each year as people stop on 101 to see the elk... but other people may NOT stop!
Further south, just past 'Stone Lagoon' is the 'Elk Country' RV Park.
(Used to be 'Little Red Schoolhouse RV park.)
It is quiet, lots of green, good space and often there are lots of elk just standing around between the trailers. If you can go to the 'back' of the park... in the trees... IMHO: Pretty neat.
(Remember that when you see 'Ancient Redwoods' park.)
If you spend time in the Northern Redwoods... compare them to the Redwoods down on the 'Avenue of the Giants' (old redwood highway also).
Southern Humboldt... drop the trailer... and...
Visit 'Humboldt Redwoods' park... west side of 101 at the Forks of the Eel.
May be the best 'southern' redwoods. Ave of the Giants... most all redwoods.
Lunch... Deb's south end of Redway... in the 'Majestic Shopping Center) (yeah, there is shopping center in Redway, inside joke).
Burgers/fries there are pretty good!
Shelter Cove is a must see too. Road takes off in Redway... 25 mile drive there... lots 'more' stuff to see down there.