i don't wanna have to delete my worlds just to add this mod but the cape feature breaks other mods

I'm not entirely sure what you mean by this.

If what you're asking is if you'll be able to upgrade your world to 1.17 and keep all your Trinkets:
You should definitely make a backup before you do this and place all the Trinkets you're wearing in your inventory or a chest because the slots will likely change.

I will attempt to read from the old trinket location and save trinkets but I do recommend backups, but I believe this person is talking about backporting trinkets 3.0.0