I’m not sure where this post should belong because it has to do with GE but it also has to do with SFO specifically. Please put it in the appropriate place if this is not the correct place.

I just obtained Global Entry this week and am doing research on how to use it. My home airport is SFO so I’m specifically interested in the process of returning into SFO. I’m reading about how for immigration/passport control there is a line for the kiosks for GE folks, a separate line for Mobile Passport folks, and then of course, the regular line for everyone else. But I’m also reading about how there is also an expedited line for customs for GE whereas there isn’t one for Mobile Passport.

Based on my recollection of SFO, once you get off the plane, you head to passport control, that’s where the long crowded lines are and if you have some kind of trusted traveler status (GE, MP), then you can bypass the line. After passport control you go through customs, where you hand off your customs form (the one you filled out on the plane) to a CBP officer and if you’re not selected for special baggage search, you leave the airport. So I’m not sure what the expedited customs line I hear about is.

Not seen an expedited customs line. With GE, you don't need to fill out the customs form, it's done on the GE machine. You just give the GE receipt to the customs officer instead.

The customs line forms in the baggage carousels area. The last few times I returned at SFO, a sign split this into two lines, GE and non-GE. The customs officer(s) collecting slips would pull from either line, and typically the GE line is far shorter.

There are some SFO experiences shared in the following thread:
They are consistent with jashsu's observations.

I think I recall now, however, I must have been lucky all the times I've come back in through SFO because while I remember handing over the customs slip to a CBP officer, I don't remember lining up, getting in line, or even seeing a line form. I just remember getting my bags off the carousel, going up to the guy, handing him my form and walking past all the unfortunate folks who were selected to have their bags checked.

Just returned to SFO from an overseas trip. Customs line for Global Entry is on the far right side and clearly marked.

This is, I believe, for Terminal A. IIRC, the kiosks are on the far left side for Terminal G.

I was referring to Terminal G.

Global Entry kiosks: Far left
Customs line for Global Entry: Far right