Hi cactusfan,
The BA lounge is fairly small but adequate and has sandwiches and snacks and alcohol.
I suspect that at about 6pm the lounge will be getting very busy as the 1930 BA flight is an A380 on some days and the lounge was not designed for that many people.
You may get asked to to the AF lounge anyway ( capacity issues) but the AF lounge is likely to be quieter anyway.
The SFO BA lounge is due to be expanded but there is no timescale.
Regards
TBS
PS There is also the Cathay Pacific lounge in the terminal ( which as an AA Exec Plat you should be able to get in) but from;
https://www.oneworld.com/ffp/lounge-...eaccess/SFO/-1
It does not look like it is open at that time