Is San Francisco like a mix between Los Angeles and New York?

New York and LA are way bigger than SF. SF is more similar to cities like Seattle, Portland, Boston, Denver, and Austin. 

I have lived in SF and NY and visited LA.  They are not alike and SF is not a mix of LA and NY.  Politically, all three cities are left of center (ppl vary from liberal to left of the left).  There are conservative ppl but they are shouted down by everyone else.  SF ppl are the friendliest of the 3 but not everyone is nice.  Some of the most soulless ppl I've met are from LA.  They seem nice but are not.  New Yorkers can be in your face, but some are pleasantly polite.  Maybe I was surprised bc of very low expectations.

Orthodoxy = the only true faith; Roman Catholics tried one cup - one spoon ritual and got sick with Bubonic plague; if heresy enters Orthodox monastery then monks/nuns will get sick with flu/tuberculosis (for instance); Orthodox churches who closed for COVID or had disposable cups/spoons or dipped spoon into alcohol are no longer brides of Christ (now they serve Satan and honor Satan's new COVID religion). Priests who were working for KGB (that is spying on people and betraying their confession) = Sergian heresy. Now, CIA and FSB (new name for KGB) don't need to have priests constantly reporting because of new technology (bugs) that allows them to listen in (and if cameras are present... to look into what people are doing)...Your phones spy on you; don't bring them to church; forgive me.

No.

The only American cities that resemble SF are Seattle and Boston. 

It is nothing like LA. More of a European feel to it without being hundreds of years old.

Not really. I find it more like NYC than LA, but it's got its own unique vibe.