this is my standard approach to tackling task force, facing their direction or opposite direction doesnt matter much. The leading heavy cruiser T1 is always shot at first, then immediately lock T2 and hammer away at the TDC settings and get a good setting asap.
with proctice on TDC now i can shoot at both the target with fast torp settings, before this i have to shot at T1 using slow torp and T2 using fast torp to allow time to set TDC.
After both ships are fired at using 2-3 torp each (depends, Takao usually need just 2, Mogami needs 3, usually). I will lock T3 and see how it reacts to the ensuing chaos, most of the time the surrounding dessies/merchants will go ape****s and block its way, thats a good time to lob in some opportunity shots with front or tail tubes.
some destroyers that presents itself nice enough (or threatening enough) will get it also, some of them has nice tonnage. (2300-2700ton).
having crews with nice competance (nice stats) and setting silent runnning + battlestation do help to make the boat stealthier somewhat despite being at full stop. Setting silent running will stop them auto-reloading which is not good at enemy presence.
In this game the destroyer seems not being able to detect you so well when u are at periscope depth and at full stop. Not sure about this at later point in the war though (havent reached that part yet).
after all fish are delivered i dive straight to max depth before turning on 0.5 or 1 knot to slip away.