[Rearview mirror wiring?]

Yes, it's switched. My dashcam uses a USB mini connection so I used this cable to convert the voltage and get the right plug: https://www.amazon.com/gp/product/B07R7JGCL1

The thick part fit inside the cover so I just have the end sticking out.

[Rearview mirror wiring?]

No problem. I had also taken a picture after I popped the cover off, which might help with where to pry. Also, I ended up running the USB tap I bought out the bottom of the cover where the mirror is, there's plenty of room for a cord there.

 

[Rearview mirror wiring?]

I'd been meaning to upload this for a while. I wanted to mount a dash camera on my GT so I probed the wires in the mirror harness to find out which were hot. Take a look at the picture to make sure you're tapping the right ones, but black is negative and white is positive. It's very easy to get access to all this, just pry around the edge of the panel that goes from the headliner to the mirror and it pops right off. I've been running my dash cam with this tap for a few months with no issues.