Kickdown system education needed

[PbFut]

After 50+ years of hot rodding, this is my first automatic transmission I’ve owned. After doing some research I am not 100% sure on a few details of the TH350 kickdown system. As I understand it, there are 2 switches, so to speak, that will drop the transmission down from drive to 2nd. One is the vacuum module that, as I understand, limits the line pressure in the transmission to delay shifting further up the RPM range or down shifting when a low vacuum state is achieved under heavy engine load. I am guessing there is some sort of mechanical weight governor as well to work in conjunction with the vacuum module. The kickdown cable is a little less clear to me. Does the cable modify the vacuum signal which in turn affects line pressure and ultimately shifting? Or, is there a second valve in the pressure line adjusted by the kickdown cable directly. Is this kickdown cable system variable or like an on off switch closing a valve at the last bit of throttle travel?
The modifications I am currently in the middle of will need to eliminate the kickdown cable. Can I use a micro switch to trigger a solenoid activated vacuum valve to close the vacuum line to the module and get the same down shift result? Is this how a TH400 works, given there is an electrical switch involved with that transmission?