Hi Frank,
Those explanations are clear but I cannot find from where they are coming. The doc you mentioned in Rune > Settings (http://www.runeaudio.com/documentation/runeui/settings/) is different and less detailed.
Just for my info: why all the lines are commented in config.txt. Does it consume memory or cpu if we load them all? The idea is to allow the users to select their DAC card directly in the Rune config UI without tinkering manually system files. Another solution could be to select the card via the UI, then to update automatically the boot.txt file and to warn the user that the system will reboot.
In fact the user shouldn't have to do twice the same thing: the configuration should be done manually OR via the UI, but not both. This is not intuitive nor logical. This is just - I hope - a constructive remark.
Matock