For my second fan I just set plainly this:
M106 P2 S0
it is working as wanted now: off as standard, and can be controlled when needed.
Clarification: the fan0 is also working great, maybe I explained it wrong:
. fan0 is off
. heater1 gets to at least 45°
. fan0 starts running
. heater1 gets under 45°
. fan0 stops running
That is this line: M106 P0 S1 I0 F500 H1 T45
So except for my blown mosfet on Fan1, everything here is solved, again sorry pro3d but much much thanks for your help!