the ride from SD to Big Sur along the coast is not the time consuming one. I would certainly opt for that. Even riding the 101 instead of the 1 in some sections will save you some time if you really think you need to rush. But that would mostly just cut out LA traffic. Depending on what time you leave might also play a role in this.
After Big Sur, the ride up the 1 can be pretty slow due to the curvy road and slow moving traffic. Its a bitchin ride though!
I'd say day one ride the coast for sure, allow for proper timing and it should be an easy one day on a bike as comfy and big as the GS. And if you start running late on day 1, you can always find a place to sleep in Cambria. Its about 75 mi south of Big Sur and has lots of great places to stay, and i think even a few camp grounds.
Day 2, I'd debate it, i've never gone much past Frisco on the 1, so i cant offer much input here.
Either way, have fun!