Hopefully I'm not overstepping my bounds as this is Erik's territory, but I think one can conclude even from the video he posted, that the new Taigen sound boards are not backwards compatible with the existing Taigen MFU. They need a control signal in order to operate and the existing Taigen MFU knows nothing about that signal and doesn't have a connector for it anyway.
I'll let Erik speak to the other questions!
Jerry, your list of items required is a little too long. It would not be possible or even make sense to use the Taigen MFU and the Open Panzer TCB together. Both are MFUs (multi-function units). Choose which one you like. From there, if you are using the TCB, you do need to add the other items on your list: hobby receiver, motor control board, and sound unit.
The reason Erik posted this new info was simply to say the upcoming standalone Taigen sound units which were designed for the new Taigen MFUs, will also work with the TCB. That is the advantage of an open software under active development, we are free to add features at any time. A few weeks ago the TCB could only produce sound with a Bendini device. Now the TCB also works with the new Taigen sound unit, take your pick. A few months from now - who knows what other options will be available.