I’m looking to get from San Francisco to Seattle and Olympic National Park and have two different options in mind; either drive the PCH south over around 3 days (is this long enough to take in all the stops and do a bit of hiking on the way?), spend a couple of days in San Diego and then fly from either San Diego or LA to Seattle, or drive north from San Francisco, taking a day in Shasta Trinity national forest and a full day at Crater lake, then heading up the Oregon/Washington coast, probably to Olympic National Park first rather than Seattle.
Given that my priorities are to take the journey slowly and spend a decent amount of time hiking rather than being in a car for 10 hours per day, which option sounds better? Ultimately I’ve heard/read that the south California coast is unparalleled; how does the Oregon coast compare, and does the greater variety of national/state parks in NoCal and Oregon justify missing out on the SoCal coast? Unfortunately I can’t incorporate both stretches into one journey!
tl;dr NoCal/OR coast + Crater Lake or PCH from SF to LA?

Any advice on either of these options would be greatly appreciated! Thanks!

When is your trip? Hwy 1 is still closed 2 hours south of Monterey until the end of July so you will need to detour inland for part of the journey if you travel before then.

Does the trip have to start in San Francisco? Can you fly to PDX or SEA and drive US 101 southbound? I like hiking in Oregon and Washington a lot more than California.
If you can make a loop through Oregon and northern California you can include Crater Lake on your return to Portland or Seattle..
Another option if you have to start in the San Francisco area would be to take the Amtrak Coast Starlight north to Portland and rent a car there.

If you decide to drive the coast south from SF, I'd stop in Santa Barbara and fly to Seattle from there. If hiking is a priority, you could continue to L.A., do some trails in the Santa Monica Mountains and fly to Seattle from Burbank or LAX. I wouldn't try to squeeze San Diego into the time you have.

But check the car rental for any one-way surcharge. Also, most lodging right on the coast will have a 2-night minimum stay requirement Thursday or Friday to Sunday. If your trip is anytime close to July 4th, look for lodging ASAP.

Thanks for the advice and the cautions everyone, unfortunately due to a couple of constraints the trip does have to start and end in Seattle, and there isn’t really the option to fly or take a train in between. (I guess I should be thankful for being able to do part of this trip at all rather than being greedy and wishing I could do the whole thing!)
It’ll be around mid August when I’m out there, so the road closure shouldn’t be an issue, but thanks for the heads up!

Even though Hwy. 1 at the landslide is due to open at the end of July, there are cautions about lane reductions and delays for several weeks thereafter because of on-going road works.

You should immediately look into lodging availability for the various places on your different itineraries. National parks, coastal towns, etc., get booked early, sometimes a year in advance. In mid-August, all of the places you mention will be very popular.

Actually, the central coast is the really magnificent part. The Oregon coast is also spectacular.