Mixing Dolby Atmos in Logic Pro

Hey everyone- I've been interested in learning to mix music in Atmos in Logic. I started by watching every YouTube video I could find about the subject, and I've also read everything the Logic Pro manual says about it, and checked out the Logic demo project mixed in "Spatial Audio".

I've learned a lot, but I feel like there's a TON I still don't understand. So I have 2 main questions-

1. Does anyone know any good resources for learning more about mixing Atmos in Logic?
2. Why is it that, while the Dolby Renderer plugin monitoring format is set to Apple Renderer, the levels I'm getting from the Level Meter plugin are different from the Master track? I'm including screenshots for clarification. I know that only surround "bed" tracks are affected by plugins on the master track before the Dolby Renderer, and that they don't affect 3D Object tracks; so is the meter the Master track only showing the sum of all of the surround bed tracks and not the 3D Objects?

As per these screenshots, the Level meter is reading 1.4 and 2.2 for the LR output, but the Master channel is showing -1.0. This is Logic's demo project by the way, so I'm confused why it would be clipping, if this is a finished mix.

Clearly I'm missing something; any info on this would be much appreciated!