[Music Lover]

That is correct. As far as the issue with book mode, what do you mean when you say you switch from "Book Mode to Follower Mode"? There isn't an option to do that in the settings at the moment... Or are you just saying you are disconnecting the leader, but the followers aren't responding correctly to the disconnect? The cell phone is going to use a fair amount more energy, but I can't give some kind of definitive measure as it depends on too many variables. I haven't measured the increased power consumption across different device models while using the "Connect Tablets" feature, so I can't accurately answer that question either, as it may vary significantly between different Android versions (and I support Android 4.0.3 all the way up to the latest). Your phone will not use any extra data so long as the other devices aren't trying to access the internet to download a bunch of stuff. You can go into the WiFi settings on each device and make sure your phone hotspot is set up as a Metered network (it's under Advanced when you tap on the settings for a particular WiFi network).

Mike