As far as I can tell, you pretty much understand what the different galleries are all about.
The only things I would comment on are, the Private Galleries members create can have more than just the creator of the gallery viewing it. IOW, if you want to create a gallery to show specific people what you're working on, you create it, and add the others as having permission to view it. I haven't done it myself since last year, so don't recall the absolute specifics, but you can have a private gallery with more than one member viewing it. It just wouldn't be available for public viewing by all members.
OK, I just thought of something, and that is, I may have been able to do so because I am a CV-Bee, so someone who isn't a CV-Bee who has created a Private gallery specific other members can view would confirm that's possible, then you'll have your answer as far as that goes.
The only other thing I'd like to comment on is the HiveWire galleries. The CV-Bees as a group don't make a decision on whether to accept an entry, in fact, I'm not sure exactly who does make that decision, as I've never uploaded anything for inclusion in the HiveWire monthly galleries. Perhaps someone else can add further information about this.