tactical sub fire mechanics

Are all similar units affected?

As far as I know if the missile silo, and not the missile built on it, is used to target a unit the silo will fire all currently available missiles at the target.
So if you for example have a Napalm already built and a tactical nuke Eos on 1% it will fire both, Napalm right away and Eos after it finishes building.

Tested this a little, missile silo works as I said previously.
Scylla however does not 'lose' target after it fires a missile, but keeps locked on until target either goes out of direct or radar sight and keeps firing, and considering that tac nuke travel time is longer than it's reload time it will overkill, or keep shooting at the target until either target dies or it runs out of ammo.
Great if you got a terraform wall and enemy doesn't know this about scylla but horrible if you're the scylla player who doesn't bother to micro it properly.
Basically Scylla acts like a regular artillery unit.

Majo i am confused, silo fires only 1 missile on my screen

Omoiyari I tested it again, it doesn't keep firing all missiles i'm just a dumb ass who left repeat order on to have a steady build order, which also included repeating order of attacking ground.
My bad.