The higher level launchers are designated either M1 or M3.
M1 uses M1 torps.
M3 uses M3 torps.

Then both M1 and M3 torps come in 3 different mods.

Mod 1 - Average speed, long range and low damage.
Mod 2 - High speed, low range and average/high damage.
Mod 3 - Slow speed, average range (still high compared to other nations) very high damage (almost sub levels of damage per torp)

M1 and M3 torps generally follow the same ternd with M3 torps having generally shorter range but more power. 

Theyre just a powerful type of japanese torpedo, they have no special attributes other than coming in a range of configurations which Sonlirain explained above.

I think simply put, if your torpedomen can use the launcher, then those torps will be available for you to use.  You don't have to do anything different or special (besides making sure you've classed to torpedoman->heavy torpedoman etc etc).