I always understood that top and tail meant the rear loco was 'dead', though may be providing Electric Train Supply. If the rear loco is powering and controllable from the front then it's push-pull working. If the rear loco can power but is not controlled from the front, then it's 'assisting' and would hace its own driver. Some steam charters/tours work like this where there is a diesel on the back supplying ETS and sometimes assisting with power on harsher gradients particularly in adverse weather conditions, giving a light shove.
These are the two most common methods, yes. "Through wired" here means that the wagons in the train have the multiple-unit control cable wired through them so that the locomotives can be connected at each end in the same way they would be if they were next to eachother. This arrangement is usually only used on wagons that are frequently push-pulled, as the through wiring is not currently standard.
