Hi DaytimeDreamer and thanks for your interest.
Regarding your questions: adapter with sync switch allows you to have bigger screen on BenQ in csync mode, for more info check my detailed explanation.
Cables are completly modified so you only connect one end to Amiga and the other to monitor and that is all.
For BenQ 912 or 702A you do not need sync inverter, direct connect is ok.
Cables do not have switch integrated, because there is less space in the 23pin case, so it would be quite hard work and time consuming task. But I can modify cable for either c-sync or h/v sync if needed.