"driving 5 miles below the (already low) speed limit"
I've driven at insane speeds in the past, I've also driven in ways that can only be described as nearly insane. I can't say I'm proud of that but I've still survived to 50 (so far). Most of the time I would describe my driving style as safe with occasional relapses 8)
I'm a Brit so I'm not familiar with Highway 1 but a quick search seems to show it is a CA road. My first virtual run on it shows three lanes on both sides, so I'll head north to SF. OK one lane. It's a provincial coastal road with adjustments.
Either get a car with a massive acceleration and overtake or enjoy the view. The speed limits are there for a good reason and I've driven a fair bit in the US (mostly FL and NY) and I don't find your limits mad. You could also lobby whoever builds roads to add another lane where you want it. On that last: in the UK we are 50 years into debating adding another lane to the A303 at some points. For some reason people are a bit wound up about the bit that goes past Stonehenge. The A303 is the super fast (lol) upgrade for the A30 (which is still there) that links London to the south west of England. It stops rather oddly at Ilminster, where it becomes the A30 again.
A relative of mine did the "compulsory purchase" of land through Hampshire, Wiltshire and Somerset for the A303, back in the day.
I live in Yeovil, Somerset, UK. To go north to say Bristol, I have two options: A37 or A372 and M5. Parts of the A37 are virtually Roman road with tarmac slapped on top 8) the A372 goes through Ilchester (formally a Roman town). Both of those roads are a bit slow but with speed limits from 30 to 60 mph. They are both delightful to drive in 3D - I love getting gears right with just the right amount of power (we have gears in our cars here 8)
Anyway, why not calm down and enjoy the view. What I've virtually seen of Highway 1 tells me that it is a road to be enjoyed and cherished and loved.