There is a good chance of needing to go from B to A on your outbound, and A to B or even C on the inbound but it's not guaranteed. If the SFO legs are on the A380 they tend to use C, but again not guaranteed. A small percentage of flights are boarded by bus.

The transit is a people mover, but there is a passageway with moving walkways below, which can be quicker. If you look in the Dashboard there's a photo guide to the walkways.

You can get from pretty much any part of T5 within 15 minutes or less, so long as a you are past security.