I have not ridden the whole SC route, but the southern half was exceedingly difficult. I personally think the winds on the coast would be a lot easier to deal with especially if you made an effort to ride early in the morning. Getting out at the crack of dawn and finishing mid day goes a long way toward minimizing the winds. Nothing makes the climbs on the SC any easier. The climbing was really extreme both in quantity and steepness.
I think that you may need to consider Covid19 in you planning even next year, but to start with I'll ignore that and just consider the route as I remember them. Both are very scenic, but in different ways. You will likely need to deal with more traffic on the coast. On the SC probably extreme heat, sparser services, and maybe forest fire smoke. Yosemite and Sequoia were pretty amazing though. If you go there I recommend spending a while in the Yosemite Valley (I don't usually stop anywhere when on tour, but it was worth 5 days there). Research the logistics of staying there as a cyclist. When we did, the drill was to stay one night in the camp where they stage folks going into the back country and get up at the crack of dawn to get in line at Camp 5 (climbers camp) to get in. The rules may have changed and 2021 may still be under Covid19 changed rules of some sort so check on what current rules are at the time of your trip.
The coast has in the past has the advantage of the hiker biker camp sites. The cheap camping in a guaranteed site with the camaraderie with other cyclists has been a big plus. Whether they will be back to normal operation in 2021 is anyone's guess. I personally wouldn't bet too much on it.
I hope I am wrong, but I expect we will still be seeing effects of Covid19 in our country in 2021. If it isn't active outbreaks, it might be budget woes that close state parks or other factors. This may affect what is open, how folks receive you, where you can stay, and generally what the touring experience is like. I am not trying to discourage you from going, but you should consider and be prepared for the fact that things may be different.
I cancelled my touring plans for this year and have not decided when I will tour again. I doubt I will get on a plane again until there is a vaccine and am not as optimistic that there will be one any time soon as the current happy talk from the white house. For now I am staying home and when I do get out it may be driving to backpacking locations rather than flying to bike touring locations.