Usually i watch films in external, icons and trails on as well as 'use recorded views'.
Lately ive started watching films (that i usually already viewed as above) from internal view, to visualize the moves from inside the cockpit. BTW, you can adjust the head positions in film viewer just like in game (arrow keys, pageup/down) and save them with f10.
If sometimes i need a better overview on the movement of the planes not only relatively to each other, but also 'over ground' (sorry cant explain that any better in english) i swich to fixed view.
Sometimes its good to get your hands on the film someone else recorded fighting you. youll see your mistakes and good moves from *his* end, that can give a good insight as well. (I know you can swich to enemy plane in viewer, but you wont get the recorded views and the movement of the control surfaces and throttle management.