Is this Part 23 Final Rule document the final regulation and what are the main improvements? Is the FAA's new Part 23 Final Rule the final new Part 23 document? Or will another document be released? The formatting is totally different and kind of a discussion can be found in all the paragraphs.

Also, what are the main improvements in this new version of Part 23?
The document itself is final, but it isn't the same thing as the actual regulations.

The same thing happened with the recent part 107 UAV regulations: the final rule document came first, then the regulations were published later. That means, at some point soon (?) the part 23 regulations will be updated to include the final rules you found, but I have no idea exactly when that will happen. The Part 23 final rule itself says:


  DATES: Effective [INSERT DATE 8 MONTHS AFTER DATE OF PUBLICATION IN
  THE FEDERAL REGISTER].


AOPA has a good explanation of what the rule changes will mean.