I think that as
wb1969 is only going to be in LAX for a couple of days then maybe the earlier flight makes more sense, just from a perspective of maximising the amount of time available to do stuff while on the west coast. I think the flight is long enough to be able to enjoy oneself - including an adult beverage or two, and a nap. Traffic from the airport to downtown LA is bad even at the best of times. I have no idea where you'll be staying but I'd certainly recommend one of the beach communities (Manhattan Beach, Hermosa Beach, Redondo Beach etc.) as I feel it's a much nicer location than downtown.
Not sure how you're planning on getting up to the bay area but Amtrak would be an option - the Coast Starlight from LA Union Station to either Emeryville or Oakland Jack London Square and then an Uber over the bridge to San Francisco. Bear in mind that long distance trains are only running 3 times a week at the moment due to COVID. I'd recommend a roomette as it's more private, you can remove your mask, you can bring your own alcohol onboard and meals are included (although the current standard of microwave TV dinners leaves a lot to be desired).
In terms of general tips, getting in to the time zone as soon as you take off is the best - so adjust your watch. That first night in LA will be critical. Staying up until 10 pm or so should mean you get a good 8 hours sleep and are up at 6 am / 7 am or thereabouts. Going to bed at 7 pm or so means you'll be awake at 3 am and it's a vicious circle from there onwards!