Ok, I suppose its nice to have room at the gate/mark, so it is generally better to come in on starboard to the left mark or on port to the right when there is lot of traffic. This decision probably is made by the moment when it is clear which mark is more windward, i.e. relatively close to the gate.

Paul, what is the advantage of gybing before? Without spi it is generally a good idea to be quite close to the other boat if you are attacking as you get a header from the winds deviated by the defender. If you tack before there is more space between the boats.

As for starboard/port encounters, due to the varying course and high velocity of both boats, it is very difficult to estimate if you on port will be able to pass the bow of a boat on starboard. Do you just wait for the last moment and then tack to starboard?