I did LA to San Fran one time and Seatle to Eureka California this year. North to South is better if your better half don't mind the cliff side. South to north keeps you back at least a lane. Pull outs are hard at times. I took a week going LA to SF north and still left much to see. Plan day in some small towns, Carmel, Hearst Castle, Monteray, San Fran needs two days. Don't be in a hurry and stop a bunch, otherwise shorten trip.
Seattle down to Oregon was half day getting to the coast. Not many roads there and some traffic in the area, plus Lemay Auto Museum and couple other sites. we went inland for about half of Oregon coast line (skipped it), then back out. Columbia River Gorge was original Kings Highway for USA and must see. We hit border of Washington and Oregon, went down gorge some but went back into Washington for Mt St Helen, then Portland for night, After Portland find old road on southern side, waterfalls and up and down the hillside in spots, must use 4 lane in spots, but stop and see the Powerhouse and Dam tour. Fish latters, more Gorge to Mt Hood, circled down staying inland to Crater Lake then back out to coast. Wild fires changed route a few times on back roads.
Coast is cold. We went first weeks of August both times and wore jackets, gloves and long sleeves. Both trips. Not like east coast all hot and sunny. Inland was 105, coast was 70 with fog everyday sometime. In morning its like riding in a cloud, grey and wet. Afternoon is good until the fog rolls in again (north trip, south stayed clear and slightly warmer on coast.)
Coast is awesome, but better sights and weather inland at times. Southern trip was completely different than northern one. Just different tempo and more to see.
Buy guidebooks and read them, a few, they list some very good spots.