You have it figured out exactly right. Only power and control system optic cable(s) to the TRIK. The TRIK is just a crazy version of the MicroController or for that matter a different way of making the front panel inside a TAP pre-amp. It runs all the functions but no audio signals are plugged into it.
They are all part of the same series of parts so either a TRIK or a MicroController can run any TAP modules inside another enclosure. For most finished products there is not reason to use either - a one box pre-amp does the 'trick' nicely so the separate controller is not needed.
If you want a TRIK for non DIY use it can run any finished pre-amp - like a 6 input Autoformer pre-amp or a Single input Autoformer pre-amp. Just adds a bit to the cost and there is NO performance difference. No real reason to do it other than for fun.
For DIY projects either the TRIK or the MicroController can be used to run the system. Just plunk down the controller anywhere in the room and run the fiber cable to the 'audio stuff in a box' hidden on a shelf in your rack. Not particularly cheap but makes a nice finished product out of a diy project without complex casework.