Hello Alfredo,
if I understand your question well I'll try an answer. Some Alembic models -the signature and the Series I and II- have a Q-switch per PU. On the SII you have a variable Q-switch per PU.
The other models (Rogue, Europa) have Q-switches and tone switches and thpse are routed for the both elements. In my early-Alembic days I had a Spoiler-bass. The q-switch influenced the sound as a whole, the other knobs were (If I remember well: volume, pan and tone control).
Standard a Q switch is 2 position: neutral and + 6db. In the signature setting (and series I) the Q switch is 3 position: neutral, +6db and +9db. I'm not sure of the specs.
Your question of sound is not answerable in text. For the q-switches: they are boosting/cutting an amount of high-tones on top of the tone setting. It's very apart as tone and really usefull. You can imagine that there is a difference if you have it separate for the two pick-ups. I don't know if -when you decide to have 2 q-s- you also need to have a tone control per PU.
Maybe there are other people here that can better answer that question. But I suggest in another box of the club.
CU
Paul