Maybe I can help with northern CA. As soon as you cross the GG bridge take the view lot exit and take a look. Lots of tourists stop there. And, heading back north, now 101 and 1, take the very next exit towards Sausalito but turn left under the freeway and follow the road up to the Marin headlands for an even greater view of the bay, SF's skyline and the bridge. Heading back to 101, follow the same road back and circle around for 101 north and ride thru the tunnel into Marin Co. Just a few miles farther take the hiway 1 cutoff thru Mill valley and over Mt Tamalpais and down to the ocean at Stinson beach. VERY curvy slow going but just spectacular scenery.
Turn north at the bottom and enjoy some of the best scenery in the state. From Bodega Bay past Bragg the road goes inland (and) along the coast but ALL of it is spectacular. A few miles past Westport/Rockport, stop where the ocean view stops and look south for the view and then ready yourself for the west coast 'dragon'. Over 20 miles of nothing but, corners and elevation changes on a tight tree lined two lane all the way to Legget where hiway 1 ends (GREAT ROAD) and then its 101 all the way north. A few miles past Garberville take the 1st Ave of the Giants exit and ride hiway 254 for about 25-30 miles right down the middle of the Avenue. Lots of places to stop and walk out among them. You won't regret it! You can spend hours walking around those giants. My son walked on a downed old growth redwood from the stump to the tip and he walked over 300 steps before he got to the end!
You can continue on the Avenue until it spills you back onto 101 or take any number of connectors back to 101 if you're in a hurry. 101, pretty much all the way from there is a four lane 'freeway' thru the redwoods with only a couple short spurts onto two lane sections. There are good eats and lodging choices in Fortuna on the west side of 101. Another tourist town nearby is Ferndale. Huge bell trees in a very old style quaint little burg and the way to the Lost Coast hiway (all 9 miles of it) and a hard road to get there. Unless you have lots of time I'd head back to 101 north. Eureka is the next 'big' town and passing thru at the north end take the Samoa road west and follow the signs to the Samoa Cookhouse. You gotta eat there! All you can eat, logger style and you eat what they're serving, no menu...and never any regrets! You can store your helmets and gear just inside their entry doors where loggers used to hang their spikes and other gear. Lots of old pics inside of old growth logging efforts way back when. They make their own bread too! Their French toast for breakfast is the best!
Heading north you'll have some nice wide open straightaways and ride in and out of ocean views past Trinidad. All great scenery if you like the color green! Near the wide spot called Klamath follow the signs to the elk preserve where I've seen 15-20 elk just a few feet from the road in their protected pasture. Great photo ops if they're out and about. If you want to continue north into OR, take 199 towards Grants Pass.
If you want to head towards Yosemite after the Avenue, hiway 36 east is a great road and takes you back, to I-5 for a quick trip south towards Yosemite. After 5 crosses 50 continue onto 99 then find your way east onto 49 all the way to 108/120 and into Yosemite. 120 is bound to be closed over the Tioga towards Nevada but 395 south is also a good drive. If 120 or others are closed, 108 or 4 (east of Big Trees SP), 88 is almost always open and except for 50 farther north, is the only way over the Sierras onto 395 and into NV if you're heading southeast into AZ.
Just remembered, off 49 take a quick drive on 4 east to Arnold to the Calaveras Big Trees SP. The north grove is open year round and takes about an hour to walk through. This is what you'll see. Spectacular old growth redwoods.