T-4 houses America West and Southwest... which probably have 80% of the flights out of PHX. Personally, I would get there no later than 6:00, and would probably be more comfortable with a 5:30 arrival.

There are two (or three) security checkpoints to get into the A and B gates, so you can generally pick the shorter one. The entire North part of the terminal is connected so, once clearing security into the north, you can get to any of the A or B gates.