Theres a whole alien race, The Ferengi, that are obsessed with something called latinum and getting as much as possible because it can’t be replicated. Other than that, it has no other useful purpose. You could replicate anything you want for free or you could get some latinum and go to a Ferengi bar and pay someone else to replicate it for you.
So basically yeah, Ferengi are also post-scarcity but since they are the capitalist caricatures of the show, they have random substance xyz so they can still have a reason for rich and poor to exist.
I’ve always considered the symbiont to be like a brain extension that while attached allows the host to access all the memories. Sort of like a flash drive adding storage to a computer. Even if the initial computer crashes the flash drive can still be plugged into a new machine and the files recovered. And, an unjoined trill (like what happened to Jadzia in Invasive Procedures can only remember what was recently accessed in the symbiont from her own brain (like a data cache).
If we are dealing with Thomas Riker or William Boimler Logic, I would say that you now have Jadzia 1 and Jadzia 2 and each is their own Dax as well.
In case number 2, I would say that most likely, as long as parallel Dax is compatible with Prime Trills, you’d still be able to pass it along to the next person. I have a feeling that the Dax’s might argue about who deserves what though. That would be/have been an interesting episode.
And as long as I am writing fan fiction, it would be interesting if Dax got some sort of worm concussion and lost certain parts of its memory. Could anything be done? Is it the same Dax without the memories of Curzon? Can we travel to an alternate timeline or back to the past to get a close approximation of the Curzon memories and somehow do a Young Frankenstein brain transfer to set everything right? Also the B story is Quark and Dr. Bashir having love triangle problems with alternate Dax or whatever.