THIS video will give you a much more in-depth review of the features and a demo of how it works than I could do right now. He only shows it opening the default nav instead of Waze, but I can tell you it opens pretty close to as quickly as it does on my Pixel 2 XL. Switching between iDrive and Android is as good as instant.
I'm not sure about Android Auto from the phone because I just installed AA on the device directly instead. There's a screen mirroring app built-in so you could have AA running on your phone and displayed on it if you wanted that.
The audio in my case is routed through the armrest aux input but the device itself handles switching inputs to and from aux and back to your satellite/am/fm radio or onboard music seamlessly.
I haven't tested phone calls with it yet but you have the choice of having your phone use either this device or the car handle calls. I haven't streamed any audio from my phone either because it's got all the apps I use onboard and it's simpler to work with it instead of the phone. I've tweaked the EQ settings enough that I'm fine with the quality but I know I'm not the most picky with that. If you prefer to keep streaming from your phone to the iDrive that's not interfered with at all.