I've been doing test all afternoon and I have found many inconsistencies.
It's easy to kill 4 to 6 bandits "cooperating" (flying straight and no evasive manevours), more than 6 bandits result in a lot of 120 hitting the same target.
But then I performed the rest of my test with just 4 bandits doing a level turn and avoiding evasive manevours.
The correct behaviour should be the one in the track "F18 TWS.trk", 4 shoots at different targets and 4 kills, but sometimes doing the same steps a few 120 hit the same target of other 120, resulting in a 2 or 3 kills, not 4.
Also, I tried to move the antena out of the targets to check if there is any inertial guidance, and sometimes 1 or 2 aim120 finds a target like in "f18 tws radar out.trk" and sometimes none of them hit a target like in "f18 tws radar out 2.trk" that seems a better behaviour. (not sure if the distance is not enough for the targets the get out of the FOV of the missile before that one enters in active phase)
TL:DR
Lots of test... and at the end I don´t know how many missiles can guide reliably in TWS.
f18 tws radar out 2.trk
f18 tws radar out.trk
f18 tws.trk