I conducted a short usability and vibration run this evening. I'm pleased with the results. The navigator screen was readable and the camera image stabilization worked. My mounting solutions are pictured below.
WRT to power options, I will have the BikeMaster power outlet (
https://bikemaster.com/12v-15a-standard-cigarette-lighter-socket-for-power-supply.html) on a bracket fastened to the top left side of the front downtube and a RAVPower battery pack (
https://www.ravpower.com/16750mah-portable-charger-power-bank-white.html, chosen for quality and built-in light) in the Burly tank bag (
http://www.classicmotorworks.com/waxed-cotton-tank-bag/). Power allocation is as follows:
(1) Garmin Zumo 660LM navigator: BikeMaster power outlet only; battery not removable for charging; cannot USB charge while in use
(2) Garmin VIRB Elite camera: USB charge port while in use; removable battery for external USB and 110V charger; spare battery
(3) LG smartphone (tunes for the road): USB charge port while in use; battery not removable for charging
(4) UClear HBC100 helmet speakers (Bluetooth from navigator and smartphone): USB charge port while NOT in use; battery not removable for charging
(5) Panasonic DMC-ZS40 camera: USB charge port when NOT in use; battery removable for external USB and 110V charging; spare battery
The (1) navigator is limited because it basically needs continuous power so must be connected to the BikeMaster power outlet. The (2) camera is very flexible because it can run for an hour on internal battery or from RAVpower battery pack or spare battery. The (3) smartphone has multi-day battery life and can be recharged from RAVpower battery pack or USB adapter plugged into BikeMaster power outlet. The (4) speakers can run for a day but must be recharged overnight from RAVpower battery pack or USB adapter plugged into BikeMaster power outlet. The (5) camera is fairly flexible because it can run for several hours on internal battery or from spare battery and when not in use can be recharged from RAVpower battery pack or USB adapter plugged into BikeMaster power outlet.
From my perspective, I have a full spectrum solution which integrates nicely into the Royal Enfield's classic looks.