I have a plex setup too, using Prologue.

I never listen to audiobooks using Plex, and prologue manages listening state just fine for me.

Your instance is it’s own thing and will only push data that’s from communities created on your instance to others.

However, since your instance will have limited users, it will consume fewer resources and your browsing experience would be faster.

I’m not sure of where the limits are on the pushing side of things. If people from a lot of instances are subscribed to a particular community in an instance, there is a lot of outgoing data from there. This is something I’m curious about.