Pacnews are meant to be manually inspected and then incorporated or deleted as needed.
It would be a bit difficult to provide an overview of each of your pacnew files .. and it is dependent on the local system/needs/etc.
Though I could mention that the mirrorlist files are probably mostly unimportant due to ranking tools like rate-mirrors.
But I might guess that somewhere between mkinitcpio and limine and snapper that these unresolved pacnews might be related to your ‘i update and it breaks’ situation. Part of updates on Arch/Cachy is pacnews and local admin attention to them.