While I can't help you with a changelog, I can give some general advise, speaking as someone who maintains a pack independently.
* Typically, pack updates are a good thing, because it's generally updating one or more mods that really needs to be updated, either for bug fixes or feature upgrades.
* If you are playing single-player, the answer to 'should I update' is almost invariably going to be 'yes', unless the pack team specifically told you that some users might not wish to for some reason and you happen to be in that minority
* If you are playing multiplayer, then the decision really isn't yours, it is up to whomever maintains the server. If they update, you have to. If they don't update, you can't either.