Here, I have drawn a wiring diagram for the parts of the payload that will be assembled by me, rather than by the balloon vendor.  I have selected parts from a vendor that has a convenient, solderless, plug-and-play wiring system, which is daisy-chainable.  That vendor is Adafruit and the wiring system is “STEMMA QT.”  I have represented the STEMMA QT connections in this diagram with purple lines.  

There is no STEMMA QT connection for my proposed Geiger counter; for that data I must solder a 6-wire serial interface to individual sites on the data logger board; that board I will have to program with the appropriate handshake signals over the appropriate wires.  I have pasted a pinout table for the serial output, and another copy for the data’s destination input.  If the serial communication programming is too difficult for me to write, then it is possible that I may choose to abandon the Geiger counter from the launch, instead.