Sorry I couldn't respond sooner, but work was getting in the way
I believe when turned on, the HUD will display navigation information without further programming of the radio. Of course to try will determine this for sure. It makes sense though base on my past experiences. Personally, I would connect the HUD in a test configuration before taking your dash apart. From a person who's had his dash out twice, it is a fair amount of work if it turns out this is not going to work.
In regards to the configuration change, it has been my experience that changing an option setting in the IPM is automatically mirrored in the RIM and requires no direct interaction with the RIM. The BPP calibration is a separate procedure, also completed through the IPM menu options.
I suspect the 'V' series cluster will have different firmware as it is a different part number and is for a different application. It would make sense that information broadcast to it will be based upon the engine option selected through the IPM configuration.
I believe the Fog Lights not US/Can is for the rear fog lights. Even though I have enabled this, my car does not retain the last state selected during the previous ignition cycle.
As far as the "Secure Car" feature, while the module part number may be the same, the software loaded into the module when installed or replaced is different. This is not as simple as changing a setting with the Tech2. I had looked for a past member a long time back. This requires the use of GM's SPS (Service Programming System). You may be able to get a module from an '06 with a newer calibration already loaded to work, however the RCDLR is an integral part of several other systems in the vehicle and you may inherit a whole new set of problems. This component plays a key role in lock/unlock status, remote start, TPMS, etc.