It is hit or miss, but recently there have been very small wait times at SFO, maybe 10-15 minutes at most. Last time thru (a couple of weeks ago), the line was long for US citizens, so agent was putting everyone (or everyone who would listen) into the visitors line.
Unless you have a really short connection, I would not worry about immigrations lines.
I have NEVER gotten out of immigration and found that my luggage (priority tagged) was already there. So my guess is you will still have to wait for your luggage.