The US rockets are different diameter, and different warhead weights, likely different trajectories, but functionally identical. The 4.5" bazooka tube mounts are much higher drag, but this is a result of the mounting, not the rocket itself. However they only have options for bazooka tube mounts in game.
The WGr 21 is an air to air rocket, with automatic detonation after (IIRC) 1000m of travel, meaning you must factor the velocity of your target in your launch timing. They are also fairly high damage vs ground targets as far as rockets go, but the mounts are very high drag.
The PzB-1 rockets on the 190F8 are shaped charge anti-tank rockets, capable of taking out any tank in the game (Tiger II included). Most can be attacked from any angle, though the Tiger II's thick frontal armor may defeat the warhead, especially if they impact at an off angle, as the turret especially is fairly close to the maximum penetration. They fire two rockets from each side before alternating wings.
They don't do much damage to structures, but are fantastic at deacking due to their high number, and can almost completely deack a ship if ripple fired.
SAP is semi-armor piercing, they have 125% the damage, but only 50% of the blast radius of GP bombs.
GP is general purpose.
