The trend in your buses seems to still be doubledeckers ,open top, hop on and hop off in San Francisco.
I only recommend 'Big Bus', with some reservations, as some of the other doubledeckers bus companies are still using London very old buses instead of new ones !!
Otherwise, there is a new big bus, 45ft, 50+ seats with restroom bus company in Frisco, STORER from Modesto.
Again, not nearly as good as that Seattle company that folded, but trying to do good, along with Mercury and a few others.
Lots of medium and large bus companies have specialized.
Minibus 'MyWay' seems to only have Japanese drivers hauling Japanese guests, very briefly to and from Yosemite Valley on day trips.
Lassen bus has mostly asian drivers.
Kings has mostly asian drivers.
Japanese-Am. Coach 21 hauls a lot of Japanese with mostly asian drivers.
The other bus trend I see in SF is the shift from full size buses, 45fters, some with front and rear steering to get around the City, to much smaller buses and vans.
Great Pacific has been a leader in quality tours in English and many foreign languages for many years with excellent driver-guides able to drive almost anywhere in central California.
A new company is the Love Bus, with old VW vans and fantastic hippie cheerful paint jobs and very good driver-guides.
Another new 15 passenger(1 driver and 14 guests) Ford Transit van charter bus company is Chariot, who I work for. Their vans are better than Mercedes standard Sprinters and some are twin turbo!! Ford just bought Chariot so I hope it continues to grow very fast.
I wish I could recommend a bicycle tour company for sf as bicycling is Booming due to our Mayor and his safer new multicolor wide bike lanes to the super-famous Golden Gate Bridge or the very large and daytime only!, wonderfully varied, Golden Gate Park, but I don't know them well.
This is just one person's opinion, mine. I love love love Lake Tahoe.
If you come to SF this year ,2017, after a very wet Winter , it should be a good year for Yosemite Valley waterfalls !! And the 70 pax, open air ,slow tram, the Wonderful $25 ,2 hr 'Valley Tour Tram' !!
Best wishes, and Enjoy !!
