This is a trivial thing to test. Open a new model, change the first mixer to complex, 2 mixers, set them to use the same input, trim on on one and off on the other, and make the second one use a switch. Then hit the switch and see what happens.
To save you the trouble (I wanted to know), if a mixer is disable, it's trim isn't applied.
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My remotely piloted vehicle ("drone") is a yacht.