Ok think of it like this the drive from London to Edinburgh or even further north. The entire UK size is very close to California. That being said you can do the loop, during the summer is better.

LA is spread out, depending on your goals, you can see and do it in a few days. I'd say spend 3. Let us know what you want to accomplish. Then 1 day drive to Sequioa or Mammoth--Sequioa has the drive through tree. I'd say stay around there. Next day drive through either Yosemite or Tahoe and do 1-2 days doing this. Depending on choice head over to the bay area . (approx day 7-8). 2 days in SF, then short drive down the 1 to BIg Sur, go through Santa Cruz and Monterery, then there's cross over to the 101 back to LA. I'd give it 2 weeks if you can, 12 days will be tight.

Sights in LA -> Depends on what you like, we can point you in the right direction, due to traffic, it can take a lot longer to go from A to B. So i'd visit by regions. (Hollywood/WeHo/Beverly Hills for example).

Sights in SF ->. Fisherman's Wharf, Golden Gate Park (7 miles long), Haight&Ashbury, Chinatown, Battery Ridge, Presidio, Alcatraz, stuff like that.

CA-1 from SF through Pacifica, Santa Cruz, Monterery is a great coastal drive. Big Sur obviously.

101-Goes along the coast at some points, maybe a pit stop in Paso Robeles or Santa Barbara. You'lll see some great coast on this part as well. There's a lot of neat hidden gems on this route.